Memristor and Robert William Jameson: Difference between pages
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[[Image:Leander Starr Jameson01.jpg|thumb|<center>Robert William Jameson]] |
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[[Image:Memristor.jpg|thumb|right|225px|This is one of the first images of a memristor, synthesised at HP labs. It shows an image of a [[Electronic circuit|circuit]] with 17 memristors captured by an [[atomic force microscope]]. The wires are 50 nm - about 150 atoms - wide.<ref>[http://www.electronicsweekly.com/Articles/2008/05/02/43658/hp-nano-device-implements-memristor.htm Bush S, "HP nano device implements memristor", ''Electronics Weekly'' 2008-05-02]</ref> Each memristor is composed of two layers of [[titanium dioxide]], of different [[resistivity|resistivities]], connected to [[wire]] [[electrode]]s. As [[electric current]] is passed through the device, the boundary between the layers moves, changing the net resistance of the device. This change may be used to record information.<ref>Michael Kanellos [http://www.news.com/8301-10784_3-9932054-7.html "HP makes memory from a once-theoretical circuit"] 2008-04-30 (Blog entry-not a [[WP:RS|reliable source]])</ref>]] |
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[[Image:Leander Starr Jameson02.jpg|thumb|<center>Christian Pringle]] |
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'''Memristors''' {{IPA|/memˈrɪstɚ/}} ("memory resistors") are a class of [[Passive_circuit_element|passive]] two-terminal [[circuit element]]s that maintain a [[function (mathematics)|function]]al relationship between the time [[integral]]s of [[electric current|current]] and [[voltage]]. This results in [[electrical resistance|resistance]] varying according to the device's '''memristance''' function. Specifically engineered memristors provide controllable resistance useful for switching current. The memristor is a special case in so-called "memristive systems", a class of [[mathematical model]]s useful for certain empirically observed phenomena, such as the firing of [[neuron]]s<ref name="chua76">Chua, L.O., and Kang, S.M., Memristive Devices and Systems, Proceedings of the IEEE 64, 206, 1976</ref>. The definition of the memristor is based solely on fundamental circuit variables, similar to the [[resistor]], [[capacitor]], and [[inductor]]. Unlike those more familiar elements, the necessarily nonlinear memristors may be described by any of a variety of time-varying functions. As a result, memristors do not belong to [[LTI system theory|linear time-invariant (LTI)]] circuit models. A linear time-invariant memristor is simply a conventional resistor.<ref>Chua, p. 511: ... In the very special case where the memristor Φ-q curve is a straight line, ... the memristor reduces to a linear time-invariant resistor.</ref> |
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'''Robert William Jameson''', WS (1805–1868): A Writer to the Signet in [[Edinburgh]], Town Councillor, newspaper Editor, poet and playwright, Robert William Jameson was the father of Sir [[Leander Starr Jameson]], South African statesman and prime minister, and the nephew of Professor [[Robert Jameson]] of the [[University of Edinburgh]]. Born in Edinburgh in 1805, Robert William was the son of Thomas Jameson, a wealthy [[shipowner]], [[merchant]] and [[burgess]] of the city of Edinburgh, as recorded in Colvin, Vol. 1: 1-2 (1922). Colvin writes of Robert William's father and grandfather, both of whom were named Thomas Jameson, that: |
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"These Jamesons came, so the tradition goes, from the [[Shetland Islands]]; and both their origin and their [[Crest (heraldry)|crest]], a ship in full sail, with ''Sine Metu'' for motto, suggest that they once followed a seafaring life. But they had been long settled in [[Leith]] and Edinburgh." (Colvin, 1922, Vol.1:1). |
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Memristor theory was formulated and named by [[Leon Chua]] in a 1971 paper. Chua strongly believed that a fourth device existed to provide conceptual symmetry with the [[resistor]], [[inductor]], and [[capacitor]]. This symmetry follows from the description of basic passive circuit elements as defined by a relation between two of the four fundamental circuit variables, namely voltage, current, charge and flux<ref>Shearer, J.L., Murphy, A.T., and Richardson, H.H., Introduction to systems dynamics, Addison-Wesley, Reading, Mass., 1967. Figure 4.4.</ref>. A device linking charge and flux (themselves defined as time integrals of current and voltage), which would be the memristor, was still hypothetical at the time. He did acknowledge that other scientists had already used fixed nonlinear flux-charge relationships.<ref name="chua71"> |
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{{citation |
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|last=Chua |
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|first=Leon O |
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|title=Memristor—The Missing Circuit Element |
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|journal=IEEE Transactions on Circuit Theory |
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|volume=CT-18 |
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|issue=5 |
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|pages=507-519 |
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|date=September 1971 |
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|year=1971 |
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|url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1083337 |
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}}</ref> |
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However, it would not be until thirty-seven years later, on [[April 30]], [[2008]], that a team at [[HP Labs]] led by the scientist [[R. Stanley Williams]] would announce the discovery of a switching memristor. Based on a [[thin film]] of [[titanium dioxide]], it has been presented as an approximately ideal device.<ref name="Nature08"> |
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{{citation |
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|last=Tour |first=James M |
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|last2=He |first2=Tao |
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|title=Electronics: The fourth element |
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|journal=Nature |
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|volume=453 |
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|pages=42-43 |
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|year=2008 |
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|url=http://www.nature.com/nature/journal/v453/n7191/full/453042a.html |
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|doi=10.1038/453042a |
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}} |
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</ref><ref name="Williams08"> |
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{{citation |
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|last=Strukov|first=Dmitri B |
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|last2=Snider|first2=Gregory S |
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|last3=Stewart|first3=Duncan R |
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|last4=Williams|first4=Stanley R |
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|title=The missing memristor found |
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|journal=Nature |
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|volume=453 |
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|pages=80-83 |
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|year=2008 |
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|doi=10.1038/nature06932 |
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|url=http://www.nature.com/nature/journal/v453/n7191/full/nature06932.html}}</ref><ref> |
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{{Cite web |
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|url=http://technology.newscientist.com/article/dn13812-engineers-find-missing-link-of-electronics.html |
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|title=Engineers find 'missing link' of electronics |
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|last=Marks |
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|first=Paul |
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|publisher=New Scientist |
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|date=[[2008-04-30]] |
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|accessdate=2008-04-30}} See also: {{Cite web |
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|url=http://www.physorg.com/news128786808.html |
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|title=Researchers Prove Existence of New Basic Element for Electronic Circuits -- Memristor' |
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|publisher=Physorg.com |
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|date=[[2008-04-30]] |
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|accessdate=2008-04-30}}</ref> |
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Being much simpler than currently popular [[MOSFET]] switches and also able to implement one [[bit]] of [[non-volatile memory|non-volatile]] [[Computer data storage|memory]] in a single device, memristors may enable [[nanoscale]] [[computer]] technology.<ref>However, as passive elements, they are incapable of [[amplification]]; moreover, it is impossible to construct [[digital logic]] entirely from memristors.</ref> Chua also speculates that they may be useful in the construction of [[artificial neural network]]s.<ref name="EETimes">{{Cite web| |
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|url=http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=207403521 |
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|title='Missing link' memristor created |
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|publisher=EETimes |
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|date=[[2008-04-30]] |
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|accessdate=2008-04-30}}</ref><!-- when did Chua say that? http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=207403521&pgno=2 In 1971? At the HP talk a few years ago? two weeks ago when informed? now? --> |
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In 1835, Robert William Jameson married Christian Pringle, daughter of [[Major-General]] Pringle of Symington and his wife Christian Watson. The Jamesons had eleven children, of whom Leander Starr was the youngest, born on February 9th, 1853. |
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== Memristor theory == |
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[[Image:Memristor-Symbol.svg|right|70px|thumb|Memristor symbol.]] |
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The memristor is formally defined<ref name="chua71"/> as a two-terminal element in which the [[Magnetic Flux#Magnetic flux through an open surface|magnetic flux]] Φ<sub>m</sub> between the terminals is a function of the amount of [[electric charge]] ''q'' that has passed through the device. Each memristor is characterized by its '''memristance''' function describing the charge-dependent rate of change of flux with charge. |
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Having first pursued a career as a Writer to the [[Signet]] in Edinburgh, Robert William's interest in journalism was recognised by his Whig friend and patron the [[Earl]] of Stair, who in 1954 made him [[Editing|Editor]] of the ''Wigtownshire Free Press'', the headquarters of which was based in [[Stranraer]], to which the family moved from Edinburgh, remaining there until 1860. |
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: <math>M(q)=\frac{\mathrm d\Phi_m}{\mathrm dq} </math> |
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Robert William was a [[Radicalization|radical]] and [[Freethought| free thinker]], author of the dramatic [[poem]] ''Nimrod'', published in 1848 and of the play ''Timolean'', a tragedy in five acts, published and performed at the [[Adelphi Theatre]] in Edinburgh in 1852. ''Timolean'', inspired by liberal anti-slavery views of the era, was popular with audiences and ran to a second edition within the first year of publication. In 1854 Jameson published the novel ''The Curse of Gold''. |
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Noting from [[Faraday's law of induction]] that magnetic flux is simply the time integral of voltage <ref>{{cite book|first=Heinz |last=Knoepfel|title=Pulsed high magnetic fields|location=New York|publisher= North-Holland|year=1970|pages=p. 37, Eq. (2.80)}}.</ref>, and charge is the time integral of current, we may write the more convenient form |
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Writing for ''The Scotsman'' in 1922, W.Forbes Gray observed of Robert William Jameson that: |
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: <math>M(q)=\frac{\mathrm d\Phi_m/\mathrm dt}{\mathrm dq/\mathrm dt}=\frac{V}{I}</math> |
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"There was probably no better known man in Edinburgh in the earlier part of the last century than Robert William Jameson, W.S., the father of the South African statesman whose biography is reviewed in your columns to-day. When the agitation for Parliamentary and municipal reform was at its height, Jameson, who was a sturdy Radical and a violent opponent of the Corn Law, ranged himself alongside of Adam Black, and was able as well as indefatigable in his advocacy of the policy of the 'clean slate'. Lord Chancellor Campbell considered Jameson the best hustings speaker he ever heard. Jameson was prominent at most of the public meetings of that time, and when the citizens of Edinburgh gave their feelings over the rejection of the first Reform Bill by the [[House of Lords]], Jameson was one of the speakers at a mass meeting in the King's Park, attended by about 50,000 people. He was also an ardent municipal reformer, and was among those chosen at the first election of the reformed [[Town Council]] of Edinburgh. In 1835 Councillor Jameson opposed a proposal that the College Committee of the Town Council should supervise the teaching given in the [[University]]." |
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It can be inferred from this that memristance is simply charge-dependent [[electrical resistance|resistance]]. If ''M''(''q(t)'') is a constant, then we obtain [[Ohm's Law]] ''R(t)'' = ''V(t)''/''I(t)''. If ''M''(''q(t)'') is nontrivial, however, the equation is ''not'' equivalent because ''q(t)'' and ''M''(''q(t)'') will vary with time. Solving for voltage as a function of time we obtain |
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Robert William and his family moved to [[Chelsea, London|Chelsea]] and [[Kensington]] in [[London]] in 1861, where he died in 1868. |
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: <math>V(t) =\ M(q(t)) I(t)</math> |
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== References: == |
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This equation reveals that memristance defines a linear relationship between current and voltage, as long as charge does not vary. Of course, nonzero current implies instantaneously varying charge. [[Alternating current]], however, may reveal the linear dependence in circuit operation by inducing a measurable voltage without ''net'' charge movement—as long as the maximum change in ''q'' does not cause [[small signal model|much]] change in ''M''. |
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Colvin, I. (1922) ''The Life of Jameson'': in Two Volumes. London: Edward Arnold and Co. |
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Furthermore, the memristor is static if no current is applied. If ''I''(''t'') = 0, we find ''V''(''t'') = 0 and ''M''(''t'') is constant. This is the essence of the memory effect. |
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Forbes Gray, W. (1922) Sir Starr Jameson's Edinburgh Ancestry, ''The Scotsman'', Tuesday, 24th October, 1922, page 6. Available from the Archives of ''The Scotsman''. |
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The [[power consumption]] characteristic recalls that of a resistor, ''I''<sup>2</sup>''R''. |
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{{DEFAULTSORT:Jameson, Robert William}} |
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:<math>P(t) =\ I(t)V(t) =\ I^2(t) M(q(t))</math> |
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[[Category:1805 births]] |
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[[Category:1868 deaths]] |
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As long as ''M''(''q''(''t'')) varies little, such as under alternating current, the memristor will appear as a resistor. If ''M''(''q''(''t'')) increases rapidly, however, current and power consumption will quickly stop. |
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[[Category:People from Edinburgh]] |
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[[Category:Scottish journalists]] |
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=== Magnetic flux in a passive device === |
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In circuit theory, magnetic flux Φ<sub>m</sub> typically relates to [[Faraday's law of induction]], which states that the voltage in terms of energy ''gained'' around a loop ([[electromotive force]]) equals the negative derivative of the flux through the loop: |
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:<math>\mathcal E = -\mathrm d\Phi_\mathrm m/\mathrm dt</math> |
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This notion may be extended by analogy to a single passive device. If the circuit is composed of passive devices, then the total flux is equal to the sum of the flux components due to each device. For example, a simple wire loop with low resistance will have high [[flux linkage]] to an applied field as little flux is "induced" in the opposite direction. Voltage for passive devices is evaluated in terms of energy ''lost'' by a unit of charge: |
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:<math>V = \mathrm d\Phi_\mathrm m/\mathrm dt\,</math> |
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:<math>\Phi_\mathrm m = \int V\mathrm dt</math> |
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Observing that Φ<sub>m</sub> is simply equal to the integral of the potential drop between two points, we find that it may readily be calculated, for example by an [[operational amplifier]] configured as an [[integrator]]. |
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Two unintuitive concepts are at play: |
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* Magnetic flux is generated by a resistance in opposition to an applied field or electromotive force. In the [[superconductor|absence of resistance]], flux due to constant EMF increases indefinitely. The opposing flux induced in a resistor must also increase indefinitely so their sum remains finite. |
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* Any appropriate response to applied voltage may be called "magnetic flux." |
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The upshot is that a passive element may relate some variable to flux without storing a magnetic field. Indeed, a memristor always appears instantaneously as a resistor. As shown above, assuming non-[[negative resistance]], at any instant it is dissipating power from an applied EMF and thus has no outlet to dissipate a stored field into the circuit. This contrasts with an [[inductor]], for which a magnetic field stores all energy originating in the potential across its terminals, later releasing it as an electromotive force within the circuit. |
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=== Physical restrictions on ''M''(''q'') === |
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An applied constant voltage potential results in uniformly increasing Φ<sub>m</sub>. Numerically, infinite [[memory (computing)|memory]] resources, or an infinitely strong field, would be required to store a number which grows arbitrarily large. Three alternatives avoid this physical impossibility: |
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* ''M''(''q'') approaches zero, such that Φ<sub>m</sub> = ∫''M''(''q'')d''q'' = ∫''M''(''q''(''t''))''I'' d''t'' remains bounded but continues changing at an ever-decreasing rate. Eventually, this would encounter some kind of [[quantum physics|quantization]] and non-ideal behavior. |
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* ''M''(''q'') is cyclic, so that ''M''(''q'') = ''M''(''q'' − Δ''q'') for all ''q'' and some Δ''q'', e.g. sin<sup>2</sup>(''q''/''Q''). |
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* The device enters [[hysteresis]] once a certain amount of charge has passed through, or otherwise ceases to act as a memristor. |
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=== Operation as a switch === |
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For some memristors, applied current or voltage will cause a great change in resistance. Such devices may be characterized as switches by investigating the time and energy that must be spent in order to achieve a desired change in resistance. Here we will assume that the applied voltage remains constant and solve for the energy dissipation during a single switching event. For a memristor to switch from ''R''<sub>on</sub> to ''R''<sub>off</sub> in time ''T''<sub>on</sub> to ''T''<sub>off</sub>, the charge must change by ΔQ = ''Q''<sub>on</sub>−''Q''<sub>off</sub>. |
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:<math>E_{\mathrm{switch}} |
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=\ V^2\int_{T_\mathrm{off}}^{T_\mathrm{on}} \frac{\mathrm dt}{M(q(t))} |
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=\ V^2\int_{Q_\mathrm{off}}^{Q_\mathrm{on}}\frac{\mathrm dq}{I(q)M(q)} |
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=\ V^2\int_{Q_\mathrm{off}}^{Q_\mathrm{on}}\frac{\mathrm dq}{V(q)} =\ V\Delta Q </math> |
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To arrive at the final expression, substitute ''V''=''I''(''q'')''M''(''q''), and then ∫d''q''/''V'' = ∆''Q''/''V'' for constant ''V''. This power characteristic differs fundamentally from that of a [[metal oxide semiconductor]] transistor, which is a capacitor-based device. Unlike the transistor, the final state of the memristor in terms of charge does ''not'' depend on bias voltage. |
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The type of memristor described by Williams ceases to be ideal after switching over its entire resistance range and enters [[hysteresis]], also called the "hard-switching regime."<ref>Williams pp 81-82.</ref> Another kind of switch would have a cyclic ''M''(''q'') so that each ''off''-''on'' event would be followed by an ''on''-''off'' event under constant bias. Such a device would act as a memristor under all conditions, but would be less practical. |
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== Titanium dioxide memristor == |
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Interest in the memristor revived in 2008 when an experimental solid state version was reported by [[R. Stanley Williams]] of [[Hewlett Packard]].<ref>{{Cite web |
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|url=http://news.bbc.co.uk/2/hi/technology/7080772.stm |
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|title=Getting More from Moore's Law |
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|last=Fildes |
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|first=Jonathan |
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|publisher=BBC |
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|date=[[2007-11-13]] |
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|accessdate=2008-04-30}} See also: {{Cite web |
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|url=http://www.ieee-or.org/beeep/2007/sep/beeep_sep07.pdf |
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|format=PDF |
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|title=Bulletin for Electrical and Electronic Engineers of Oregon |
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|publisher=[[Institute of Electrical and Electronics Engineers]] |
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|date=September 2007 |
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|accessdate=2008-04-30}}</ref><ref>{{cite web|url=http://www.hpl.hp.com/about/bios/stanwilliams.html|title=R. Stanley Williams (HP biography)}}</ref><ref>{{cite web|url=http://www.hpl.hp.com/research/qsr/people/Stan_Williams/|title=Stan Williams, (HP biography)}}</ref> A solid-state device could not be constructed until the unusual behavior of [[nanoscale]] materials was better understood. The device neither uses magnetic flux as the theoretical memristor suggested, nor stores charge as a capacitor does, but instead achieves a resistance dependent on the history of current using a chemical mechanism. |
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The HP device is composed of a thin (5 [[nanometre|nm]]) [[titanium dioxide]] film between two [[electrode]]s. Initially, there are two layers to the film, one of which has a slight depletion of [[oxygen]] atoms. The oxygen vacancies act as [[charge carrier]]s, meaning that the depleted layer has a much lower resistance than the non-depleted layer. When an electric field is applied, the oxygen vacancies drift (see ''[[Fast ion conductor]]''), changing the boundary between the high-resistance and low-resistance layers. Thus the resistance of the film as a whole is dependent on how much charge has been passed through it in a particular direction, which is reversible by changing the direction of current.<ref name="Williams08"/> Since the HP device displays fast ion conduction at nanoscale, it is considered a [[nanoionic device]].<ref>Terabe K., Hasegawa T., Liang C., Aono M. Control of local ion transport to create unique functional nanodevices based on ionic conductors. Science and Technology of Advanced Materials 2007. V.8. P.536-542</ref> |
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Memristance is displayed only when both the doped layer and depleted layer contribute to resistance. When enough charge has passed through the memristor that the ions can no longer move, the device enters [[hysteresis]]. It ceases to integrate ''q''=∫''I''d''t'' but rather keeps ''q'' at an upper bound and ''M'' fixed, thus acting as a resistor until current is reversed. |
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Memory applications of thin-film oxides had been an area of active investigation for some time. [[IBM]] published an article in 2000 regarding structures similar to that described by Williams.<ref> |
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{{Cite web |
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|url=http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000077000001000139000001&idtype=cvips&gifs=yes |
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|title=Reproducible switching effect in thin oxide films for memory applications |
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}}</ref> [[Samsung]] has a pending U.S. patent application for several oxide-layer based switches similar to that described by Williams.<ref>{{cite web|url=http://www.google.com/patents?id=hIKiAAAAEBAJ&dq=11655193,|title=US Patent Application 11/655,193}}</ref> Williams also has a pending U.S. patent application related to the memristor construction.<ref>{{cite web|url=http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1&p=1&f=G&l=50&d=PG01&S1=20080090337.PGNR.&OS=dn/20080090337&RS=DN/20080090337,|title=US Patent Application 11/542,986}}</ref> |
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Although the HP memristor is a major discovery for electrical engineering theory, it has yet to be demonstrated in operation at practical speeds and densities. Graphs in Williams' original report show switching operation at only ~1 [[Hertz|Hz]]. Although the small dimension of the device seem to imply fast operation, the charge carriers move very slowly, with an ion [[electron mobility|mobility]] of 10<sup>−10</sup> [[centimetre|cm]]<sup>2</sup>/([[Volt|V]]·[[Second|s]]). In comparison, the highest known [[drift current|drift]] ionic mobilities occur in [[advanced superionic conductors]], such as [[rubidium silver iodide]] with about 2×10<sup>−4</sup> cm²/(V·s) conducting silver ions at [[room temperature]]. Electrons and holes in silicon have a mobility ~1000 cm²/(V·s), a figure which is essential to the performance of transistors. However, a relatively low bias of 1 volt was used, and the plots appear to be generated by a mathematical model rather than a laboratory experiment.<ref name="Williams08"/> |
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== Polymeric memristor == |
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In July 2008 Victor Erokhin and Marco P. Fontana in ''Electrochemically controlled polymeric device: a memristor (and more) found two years ago''<ref>{{cite web|url=http://eprintweb.org/S/article/cond-mat/0807.0333|title=Electrochemically controlled polymeric device: a memristor (and more) found two years ago}}</ref> claim to have developed a polymeric memristor before the titanium dioxide memristor more recently announced. |
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== Spin memristive systems == |
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A fundamentally different mechanism for memristive behavior has been proposed by [http://www.physics.ucsd.edu/~pershin/ Yuriy V. Pershin] and [http://physics.ucsd.edu/~diventra/ Massimiliano Di Ventra] in their paper “Spin memristive systems”<ref>{{cite web|url=http://eprintweb.org/S/article/cond-mat/0806.2151|title=Spin memristive systems}}</ref>. The authors show that certain types of semiconductor [[spintronic]] structures belong to a broad class of memristive systems as defined by Chua and Kang<ref name="chua76"/>. The mechanism of memristive behavior in such structures is based entirely on the electron spin degree of freedom which allows for a more convenient control than the ionic transport in nanostructures. When an external control parameter (such as voltage) is changed, the adjustment of electron spin polarization is delayed because of the diffusion and relaxation processes causing a hysteresis-type behavior. This result was anticipated in the study of spin extraction at semiconductor/ferromagnet interfaces <ref>{{citation |
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|last=Pershin |first=Yuriy V |
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|last2=Di Ventra |first2=Massimiliano |
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|title=Current-voltage characteristics of semiconductor/ferromagnet junctions in the spin-blockade regime |
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|journal=Physical Review B |
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|volume=77 |
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|pages=073301 |
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|year=2008 |
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|url=http://link.aps.org/abstract/PRB/v77/e073301 |
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|doi=10.1103/PhysRevB.77.073301 |
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}}</ref>, but was not described in terms of memristive behavior. On a short time scale, these structures behave almost as an ideal memristor<ref name="chua71"/>. This result broadens the possible range of applications of semiconductor spintronics and makes a step forward in future practical applications of the concept of memristive systems. |
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== Manganite memristive systems == |
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Although not described using the word "memristor" a study was done of bilayer oxide films based on [[manganite]] for non-volatile memory by researchers at the University of Houston in 2001<ref> |
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{{Cite web |
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|url=http://klabs.org/richcontent/MemoryContent/nvmt_symp/nvmts_2001/papers_presentations/05_electric_pulse/05_Ignatiev-foils.pdf |
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|title=A New Concept for Non-Volatile Memory: The Electric Pulse Induced Resistive Change Effect in Colossal Magnetoresistive thin Films |
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|last=Liu |
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|first=Shangqing |
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|last2=Wu |
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|first2=NaiJuan |
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|last3=Chen |
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|first3=Xin |
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|last4=Ignatiev |
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|first4=Alex |
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|date=[[2001-11-06]] |
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|accessdate=2008-10-05}} |
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</ref>. Some of the graphs indicate a tunable resistance based on the number of applied voltage pulses similar to the effects found in the titanium dioxide memristor materials described in the Nature paper "The missing memristor found". |
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== Potential applications == |
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Williams' solid-state memristors can be combined into devices called [[crossbar latch]]es, which could replace transistors in future computers, taking up a much smaller area. |
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They can also be fashioned into [[non-volatile memory|non-volatile]] solid-state memory, which would allow greater data density than hard drives with access times potentially similar to [[Dynamic random access memory|DRAM]], replacing both components.<ref> |
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{{Cite web |
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|url=http://www.news.com/8301-10784_3-9932054-7.html |
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|title=HP makes memory from a once theoretical circuit |
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|last=Kanellos |
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|first=Michael |
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|publisher=CNET News.com |
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|date=[[2008-04-30]] |
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|accessdate=2008-04-30}} |
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</ref> |
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HP prototyped a [[crossbar latch]] memory using the devices that can fit 100 [[gigabit]]s in a square centimeter.<ref name="EETimes"/> |
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For comparison, as of 2008 the highest-density [[Flash memory|flash memories]] hold 32 [[gigabit]]s. <!-- 32 Gb in how much space?? --> HP has reported that its version of the memristor is about one-tenth the speed of DRAM.<ref> |
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{{Cite web |
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|url=http://www.nytimes.com/2008/05/01/technology/01chip.html |
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|title=H.P. Reports Big Advance in Memory Chip Design |
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|last=Markoff |
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|first=John |
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|publisher=NY Times |
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|date=[[2008-05-01]] |
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|accessdate=2008-05-01}} |
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</ref> |
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The devices' resistance would be read with [[alternating current]] so that they do not affect the stored value.<ref> |
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{{Cite web |
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|url=http://arstechnica.com/news.ars/post/20080501-maintaining-moores-law-with-new-memristor-circuits.html |
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|title=Maintaining Moore's law with new memristor circuits |
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|last=Gutmann |
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|first=Ethan |
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|publisher=Ars Technica |
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|date=[[2008-05-01]] |
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|accessdate=2008-05-01}} |
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</ref> |
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Some patents related to memristors appear to include applications in programmable logic,<ref>{{US patent|7203789}}</ref> signal processing,<ref>{{US Patent|7302513}}</ref> [[neural networks]],<ref>{{US patent|7359888}}</ref> and control systems.<ref>{{US patent application|11/976927}}</ref> |
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== See also == |
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{{commoncat|Memristors}} |
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{{portalpar|Electronics|Nuvola_apps_ksim.png}} |
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*[[Integrated circuit]] |
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*[[List of emerging technologies]] |
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*[[RRAM]] |
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== References == |
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{{Reflist}} |
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== External links == |
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* [http://www.hpl.hp.com/news/2008/apr-jun/memristor_faq.html Technical FAQ by Memristor lead scientist, Stan Williams of HP Labs] May 20, 2008 |
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* [http://www.npr.org/templates/story/story.php?storyId=90289714 "Talk of the Nation" interview with co-discover Stan Williams of HP] May 10, 2008 |
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* [http://www.informationweek.com/news/hardware/processors/showArticle.jhtml?articleID=207403582 HP Reveals Memristor, The Fourth Passive Circuit Element] April 30, 2008 |
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* [http://news.bbc.co.uk/1/hi/technology/7377063.stm BBC News - Electronics' 'missing link' found] May 1, 2008 |
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* [http://www.nature.com/news/2008/080430/full/news.2008.789.html Nature News - Found: the missing circuit element] Apr 30, 2008 |
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* [http://blog.wired.com/gadgets/2008/04/scientists-prov.html Wired.com - Scientists Create First Memristor: Missing Fourth Electronic Circuit Element] April 30, 2008 |
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* [http://www.eetimes.com/news/semi/showArticle.jhtml?articleID=207403521&pgno=1 EE Times - 'Missing link' memristor created: Rewrite the textbooks?] April 30, 2008 |
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* [http://www.spectrum.ieee.org/may08/6207 IEEE Spectrum - The Mysterious Memristor, by Sally Adee] May 2008 |
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* [http://adsabs.harvard.edu/abs/1990JAP....67.3132T Solid-state thin-film memristor for electronic neural networks - Journal of Applied Physics, vol. 67] March 1990 |
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* [http://knol.google.com/k/blaise-mouttet/programmable-electronics-using/23zgknsxnlchu/2#view A knol on memristors] discussing applications in signal processing and filtering, artificial intelligence, computer/brain interfaces, etc. |
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[[Category:Electrical components]] |
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[[bn:মেম্রিস্টর]] |
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Revision as of 08:01, 11 October 2008
Robert William Jameson, WS (1805–1868): A Writer to the Signet in Edinburgh, Town Councillor, newspaper Editor, poet and playwright, Robert William Jameson was the father of Sir Leander Starr Jameson, South African statesman and prime minister, and the nephew of Professor Robert Jameson of the University of Edinburgh. Born in Edinburgh in 1805, Robert William was the son of Thomas Jameson, a wealthy shipowner, merchant and burgess of the city of Edinburgh, as recorded in Colvin, Vol. 1: 1-2 (1922). Colvin writes of Robert William's father and grandfather, both of whom were named Thomas Jameson, that:
"These Jamesons came, so the tradition goes, from the Shetland Islands; and both their origin and their crest, a ship in full sail, with Sine Metu for motto, suggest that they once followed a seafaring life. But they had been long settled in Leith and Edinburgh." (Colvin, 1922, Vol.1:1).
In 1835, Robert William Jameson married Christian Pringle, daughter of Major-General Pringle of Symington and his wife Christian Watson. The Jamesons had eleven children, of whom Leander Starr was the youngest, born on February 9th, 1853.
Having first pursued a career as a Writer to the Signet in Edinburgh, Robert William's interest in journalism was recognised by his Whig friend and patron the Earl of Stair, who in 1954 made him Editor of the Wigtownshire Free Press, the headquarters of which was based in Stranraer, to which the family moved from Edinburgh, remaining there until 1860.
Robert William was a radical and free thinker, author of the dramatic poem Nimrod, published in 1848 and of the play Timolean, a tragedy in five acts, published and performed at the Adelphi Theatre in Edinburgh in 1852. Timolean, inspired by liberal anti-slavery views of the era, was popular with audiences and ran to a second edition within the first year of publication. In 1854 Jameson published the novel The Curse of Gold.
Writing for The Scotsman in 1922, W.Forbes Gray observed of Robert William Jameson that:
"There was probably no better known man in Edinburgh in the earlier part of the last century than Robert William Jameson, W.S., the father of the South African statesman whose biography is reviewed in your columns to-day. When the agitation for Parliamentary and municipal reform was at its height, Jameson, who was a sturdy Radical and a violent opponent of the Corn Law, ranged himself alongside of Adam Black, and was able as well as indefatigable in his advocacy of the policy of the 'clean slate'. Lord Chancellor Campbell considered Jameson the best hustings speaker he ever heard. Jameson was prominent at most of the public meetings of that time, and when the citizens of Edinburgh gave their feelings over the rejection of the first Reform Bill by the House of Lords, Jameson was one of the speakers at a mass meeting in the King's Park, attended by about 50,000 people. He was also an ardent municipal reformer, and was among those chosen at the first election of the reformed Town Council of Edinburgh. In 1835 Councillor Jameson opposed a proposal that the College Committee of the Town Council should supervise the teaching given in the University."
Robert William and his family moved to Chelsea and Kensington in London in 1861, where he died in 1868.
References:
Colvin, I. (1922) The Life of Jameson: in Two Volumes. London: Edward Arnold and Co.
Forbes Gray, W. (1922) Sir Starr Jameson's Edinburgh Ancestry, The Scotsman, Tuesday, 24th October, 1922, page 6. Available from the Archives of The Scotsman.