Phase-change materials are some of the most promising materials for data-storage applications. They are already used in rewriteable optical data storage and offer great potential as an emerging non-volatile electronic memory. This review looks at the unique property combination that characterizes phase-change materials. The crystalline state often shows an octahedral-like atomic arrangement, frequently accompanied by pronounced lattice distortions and huge vacancy concentrations. This can be attributed to the chemical bonding in phase-change alloys, which is promoted by p-orbitals. From this insight, phase-change alloys with desired properties can be designed. This is demonstrated for the optical properties of phase-change alloys, in particular the contrast between the amorphous and crystalline states. The origin of the fast crystallization kinetics is also discussed.

Phase-change materials for rewriteable data storage

The development of materials whose refractive index can be optically transformed as desired, such as chalcogenide-based phase-change materials, has revolutionized the media and data storage industries by providing inexpensive, high-speed, portable and reliable platforms able to store vast quantities of data. Phase-change materials switch between two solid states--amorphous and crystalline--in response to a stimulus, such as heat, with an associated change in the physical properties of the material, including optical absorption, electrical conductance and Young's modulus. The initial applications of these materials (particularly the germanium antimony tellurium alloy Ge2Sb2Te5) exploited the reversible change in their optical properties in rewritable optical data storage technologies. More recently, the change in their electrical conductivity has also been extensively studied in the development of non-volatile phase-change memories. Here we show that by combining the optical and electronic property modulation of such materials, display and data visualization applications that go beyond data storage can be created. Using extremely thin phase-change materials and transparent conductors, we demonstrate electrically induced stable colour changes in both reflective and semi-transparent modes. Further, we show how a pixelated approach can be used in displays on both rigid and flexible films. This optoelectronic framework using low-dimensional phase-change materials has many likely applications, such as ultrafast, entirely solid-state displays with nanometre-scale pixels, semi-transparent 'smart' glasses, 'smart' contact lenses and artificial retina devices.

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An optoelectronic framework enabled by low-dimensional phase-change films

A unique class of microcrystalline semiconductor materials which can be modulated, within a crystalline phase, to assume any one of a large dynamic range of different Fermi level positions while maintaining a substantially constant band gap over the entire range, even after a modulating field has been removed. A solid state, directly overwritable, electronic and optical, non-volatile, high density, low cost, low energy, high speed, readily manufacturable, multibit single cell memory based upon the novel switching characteristics provided by said unique class of semiconductor materials, which memory exhibits orders of magnitude higher switching speeds at remarkably reduced energy levels. The novel memory of the instant invention is in turn characterized, inter alia, by numerous stable and non-volatile detectable configurations of local atomic order, which configurations can be selectively and repeatably accessed by input signals of varying levels.

Homogeneous compositions of microcrystalline semiconductor material, semiconductor devices and directly overwritable memory elements fabricated therefrom, and arrays fabricated from the memory elements

A filter device inserts into a duct having flow passing from upstream to downstream. The filter device includes fluted filter media having flutes (24) formed therein. The filter forms a seal between the outer edge of the filter and the downstream side of the duct. The filter media may be rolled or stacked in layers to match the shape of the duct.

Inline filter apparatus

A catalyst for purifying exhaust gases exhibits not only effective purifying characteristics even in a low temperature range such as immediately after an engine starts but also high exhaust gas purifying ability. In the catalyst for purifying exhaust gases of a first aspect of the invention, HC adsorbed at low temperature are released at high temperature and the released HC are purified by a catalyst metal. This catalyst for purifying exhaust gases has an excellent advantage in purifying HC at low temperature as well as excellent exhaust gas purifying ability.

Catalyst for purifying exhaust gases

A recording apparatus overwrites an input signal (s1) having pulse duration periods and pulse spacing periods to a optical disk by irradiation of a laser beam to form recording marks corresponding to the pulse duration periods. The apparatus includes detector (10) for detecting a leading edge of the pulse duration period and for producing a start signal thereupon, another detector (11) for detecting a trailing edge of the pulse duration period and for producing a stop signal thereupon, a pattern setting circuit (3) for setting a predetermined basic pattern, and a pattern generator (12) for generating the basic pattern from its beginning in response to the start signal and for terminating the generation of the basic pattern in response to the stop signal. The apparatus further includes a circuit (9, Ia, Ib, Ic, 4) for forming a modulated signal using a full or portion of the basic pattern produced from the pattern generator (12). The laser is produced by the modulated signal.

Optical information recording method

An exhaust gas filter for internal combustion engine and of honeycomb structure comprising a ceramic fiber and inorganic binder, the ceramic fiber consists mainly of Al₂O₃ and SiO₂, the inorganic binder including Al₂O₃ and SiO₂ to bind the said ceramic fiber, and the inorganic binder is of single glass phase or of mixed phase of a glass phase and a crystal phase keeping the same crystal structure in the temperature range of 20 to 1200°C, whereby, in the inorganic binder, any crystal such as quartz which produces abnormal expansion due to crystal phase transition is excluded, and occurrance of crack is prevented..

Exhaust gas filter and method for making the same

PURPOSE: To provide an optical information-recording member having excellent characteristics for repeated recording and erasing and favorable stability with time of erasing ratio and ensuring sufficient blackening (erasing) and whitening (recording) through the use of an existing semiconductor laser power, by specifying the atomic ratio of Te, Ge and Sn and concentration of Au in providing a recording layer formed of a composition of a Te-Ge-Sn-Au system. CONSTITUTION: The figure shows an appropriate range of the recording member constituted of a Te-Ge-Sn-Au system, which comprises a Te-Ge-Sn system, and the Au concentration is 1W40at% in relation to the Te-Ge-Sn composition (the Au concentration corresponds to (n) in the formula (Te x Ge y Sn z ) m Au n ). The composition (in at%) at point A is Te 93 Ge 5 Sn 2 , that at point B is Te 93 Ge 2 Sn 5 , that at point C is Te 68 Ge 2 Sn 30 , that at point D is Te 52 Ge 18 Sn 30 and that at point E is Te 52 Ge 46 Sn 20 . The composition constituting the recording layer lies in the region ABCDE on the diagram for the Te-Ge-Sn ternary system, and the Au concentration in terms of (n) in the formula (Te x Ge y Sn z ) m Au n is in the range of 1W40at%. COPYRIGHT: (C)1986,JPO&Japio

Optical information recording member

A catalyst for purifying an exhaust gas comprising a carrier substantially composed of calcium aluminate and titanium oxide. The carrier is deposited with a platinum group metal or a metal oxide capable of oxidizing reductive gases into innoxious ones. The titanium oxide is applied on the surface of the carrier or incorporated in the carrier. The carrier may further comprise a transition metal oxide showing catalytic activity. A method of making a catalyst is also disclosed in which titanium oxide is applied on the surface of a solid mass of calcium aluminate.

Catalyst for purifying exhaust gases and method for manufacturing same

A reversible optical information recording medium which permits recording, reproducing, erasing and rewriting at high speeds by means of laser beams. The reversible optical information recording medium has a recording thin film which is essentially constituted by Te-Au-O, and Ge or Se. In the system which employs Ge, the recording thin film is formed by addition of at least one selected from a group consisting of Sn, In, Bi and Sb, such as to reduce the Au content in the film composition. On the other hand, in the system which employs Se, a further improvement in the stability of the recorded signal is achievable by the addition of Ge, and an improvement in the recording/erasing sensitivities, particularly erasing sensitivity, can be enhanced by addition of at least one element selected from a group consisting of Sn, In, Bi and Sb. The recording/erasing mechanism in the reversible optical information recording medium of the invention mainly relies upon a change in the optical characteristic which in turn is caused mainly by a reversible phase change of Te. The phase change in the recording medium of the invention can be effected by a laser beam of an extremely low light power density and short irradiation time as compared with that required by the conventional optical information recording medium. This in turn permits much higher speed of recording and erasing of information over the conventional optical information recording medium.

Kunio Kimura

Papers

Optical information recording method

Exhaust gas filter and method for making the same

Optical information recording member

Catalyst for purifying exhaust gases and method for manufacturing same

Reversible optical information-recording medium