Electrically tunable metasurfaces including an array of subwavelength metasurface unit elements are presented. The unit elements include a stacked metal-insulator-metal structure within which an active phase change layer is included. A purely insulator, metal, or coexisting metal-insulator phase of the active layer can be electrically controlled to tune an amplitude and phase response of the metasurfaces. In combination with the subwavelengths dimensions of the unit elements, the phase and amplitude response can be controlled in a range from optical wavelengths to millimeter wavelength of incident light. Electrical control of the unit elements can be provided via resistive heating produced by flow of current though a top metal layer of the unit elements. Alternatively, electrical control of the unit elements can be provided via electrical field effect produced by applying a voltage differential between the top and bottom metal layers of the unit elements.

An approach to form a semiconductor structure with a multiple layer phase change material stack and four electrodes that functions as an integrated switch device. The semiconductor structure includes a sidewall spacer that is on two opposing sides of the multiple layer phase change material stack contacting an edge of each layer of the multiple layer phase change material stack. The semiconductor structure includes a pair of a first type of electrode, where each of the pair of the first type of electrode abuts each of the sidewall spacers on the two opposing sides of the multiple layer phase change material stack. A pair of a second type of electrode, where each of the second type of electrode abuts each of two other opposing sides of the multiple layer phase change material stack and contacts a heater material on outside portions of the multiple layer phase change material stack.

The invention is notably directed to a transflective display device. The device comprises a set of pixels, wherein each of the pixels comprises a portion of bi-stable, phase change material, hereafter a PCM portion, having at least two reversibly switchable states, in which it has two different values of refractive index and/or optical absorption. The device further comprises one or more spacers, optically transmissive, and extending under PCM portions of the set of pixels. One or more reflectors extend under the one or more spacers. An energization structure is in thermal or electrical communication with the PCM portions, via the one or more spacers. Moreover, a display controller is configured to selectively energize, via the energization structure, PCM portions of the pixels, so as to reversibly switch a state of a PCM portion of any of the pixels from one of its reversibly switchable states to the other. A backlight unit is furthermore configured, in the device, to allow illumination of the PCM portions through the one or more spacers. The backlight unit is controlled by a backlight unit controller, which is configured for modulating one or more physical properties of light emitted from the backlight unit. The invention is further directed to related devices and methods of operation.

Circuits and methods that enable stacking of phase change material (PCM) switches and that accommodate variations in the resistance of the resistive heater(s) of such switches. Stacking is enabled by providing isolation switches for the resistive heater(s) in a PCM switch to reduce parasitic capacitance caused by the proximity of the resistive heater(s) to the PCM region of a PCM switch. Variations in the resistance of the resistive heater(s) of a PCM switch are mitigated or eliminated by sensing the actual resistance of the resistive heater(s) and then determining a suitable adjusted electrical pulse profile for the resistive heater(s) that generates a precise thermal pulse to the PCM region, thereby reliably achieving a desired switch state while extending the life of the resistive heater(s) and the phase-change material.

A PCM cell includes a first electrode, a heater/PCM portion electrically connected to first electrode, the heater/PCM portion comprising a PCM material, a second electrode electrically connected to the PCM material, and an electrical insulator stack surrounding the projection liner. The stack includes a plurality of first layers comprised of a first material and having a plurality of first inner sides facing towards the projection liner, and a plurality of second layers alternating with the plurality of first layers, the plurality of second layers comprised of a second material that is different from the first material, and the second plurality of layers having a plurality of second inner sides facing towards the projection liner. The plurality of second inner sides that are offset from the plurality of first inner sides forming a plurality of gaps.

An apparatus comprises a phase-change material, a first electrode at a first end of the phase-change material, a second electrode at a second end of the phase-change material, and a heating element coupled to a least a given portion of the phase-change material between the first end and the second end. The apparatus also comprises a first input terminal coupled to the heating element, a second input terminal coupled to the heating element, and an output terminal coupled to the second electrode.

A phase change memory (PCM) cell includes a first electrode comprised of a first electrically conductive material, a second electrode comprised of a second electrically conductive material, and a phase change section positioned between the first electrode and the second electrode. The phase change section includes a first phase change material having a first resistance drift coefficient, and a second phase change material having a second resistance drift coefficient that is greater than the first resistance drift coefficient. An axis of the PCM cell extends between the first electrode and the second electrode, and the second phase change material is offset from the first phase change material in a direction that is perpendicular to the axis.

One example includes a method for making a switch. The method includes forming an insulating layer over a substrate. The method also includes forming a resistive heating material over the insulating layer. The method also includes depositing a thermally conductive electrically insulating barrier layer over the heating material. The method also includes forming a phase-change material (PCM) component over the barrier layer spaced apart and proximal to the resistive heating material. The method also includes forming a quench layer proximal to at least one of the resistive heating material and the PCM component. The method further includes forming conductive lines from ends of the PCM component and control lines from ends of the resistive heating material.

An apparatus comprises a phase-change material, a first electrode at a first end of the phase-change material, a second electrode at a second end of the phase-change material, and a heating element coupled to a least a given portion of the phase-change material between the first end and the second end. The apparatus also comprises a first input terminal coupled to the heating element, a second input terminal coupled to the heating element, and an output terminal coupled to the second electrode.

Techniques for controlling the programming current of a PCM-based AI device using an external resistor are provided. In one aspect, a PCM cell includes: a PCM stack, that has a bottom electrode; a heater disposed directly on the bottom electrode; a PCM unit including a first material disposed on the heater; a top electrode including a second material disposed on the PCM unit; and a resistor adjacent to the PCM stack, wherein the resistor includes a combination of the first material and the second material. A PCM device that includes at least one of the PCM cells, and a method of forming the PCM cell are also provided.