A three dimensional memory which is comprised of a plurality of stacked memory planes, each of which includes at least a continuous transparent photovoltaic-ferroelectric layer sandwiched between two continuous plane transparent electrodes. In one embodiment, the memory planes are comprised of only the photovoltaic-ferroelectric layer sandwiched between the two electrodes, and in another embodiment the ferroelectric layer and a continuous transparent photoconductive layer are sandwiched between the two electrodes.
A thermal imaging device includes detector pixels A, B, C provided by a pyroelectric layer 1 arranged between electrode structures 3 and 4. A photoconductive layer 7 is provided between the electrode structure 5 and a further electrode structure 9. The device also includes an illumination source 11 for illuminating the photoconductive layer 7 for enabling pyroelectric charge developed by the detector pixels A, B, C to be optically addressed via the electrode structure 9. Optical addressing of the detector pixels obviates the need for solid state switching connections to each pixel, providing an imaging device readily capable of large scale fabrication.
An electrically programmable, optically readable data or memory cell is configured from a thin film of ferroelectric material, such as PZT, sandwiched between a transparent top electrode and a bottom electrode. The output photoresponse, which may be a photocurrent or photo-emf, is a function of the product of the remanent polarization from a previously applied polarization voltage and the incident light intensity. The cell is useful for analog and digital data storage as well as opto-electric computing. The optical read operation is non-destructive of the remanent polarization. The cell provides a method for computing the product of stored data and incident optical data by applying an electrical signal to store data by polarizing the thin film ferroelectric material, and then applying an intensity modulated optical signal incident onto the thin film material to generate a photoresponse therein related to the product of the electrical and optical signals.
Photoresponse from a ferroelectric optical computing device, such as a memory cell or a logic switch, is increased by either illuminating the regions of the ferroelectric crystal under the electrode edges in a sandwich structure device or by aligning the principal axis of the ferroelectric crystal parallel to the linear polarization vector of the optical beam. Device density is increased by reducing the beam size using a small near-field optical fiber. Device evaluation including imprint failure susceptibility is performed by illuminating each ferroelectric optical computing device in a large array of such devices and storing the device address of any device whose response departs from a normal range.
The invention relates to a read-write optical memory comprising a plurality of juxtaposed memory cells (11), each receiving a respective light beam (3). Each memory cell contains a storage medium (10), which includes a storage element (23) having stable optical states. The storage element (23) is divided into a number of memory points, and the optical state in a given memory point can be both changed and read by means of a light beam (3) directed towards the memory point. The memory can be implemented entirely without any movable mechanical parts and has a very short read-write time and an exceptionally high storage capacity. Parallel writing and reading of multibit words is possible.
A thin-film zinc oxide varistor (10) for use in integrated circuits and the like is produced by applying a polyoxyalkylated metal complex, such as a metal alkoxycarboxylate, to a substrate (12, 14, and 16) for the formation of a dried nonohmic layer (18). The method of production includes the steps of providing a substrate and a precursor solution including a polyoxyalkylated zinc complex (P22, P24), coating a portion of the substrate with the precursor solution (P26), drying the coated substrate (P32), and crystallizing the dried thin-film zinc oxide layer (P30). The resultant crystalline zinc oxide varistor layer (18) may be doped with bismuth, yttrium, praseodymium, cobalt, antimony, manganese, silicon, chromium, titanium, potassium, dysprosium, cesium, cerium, and iron to provide a non-ohmic varistor. The varistor layer (10) is annealed at a temperature ranging from about 400 to about 1000.degree. C. to provide a layer having a thickness ranging from about 50 nanometers to about 500 nanometers and an average grain size diameter less than about 200 nanometers.
