Effect of Substrate-Thickness on Voltage Responsivity of MEMS-Based ZnO Pyroelectric Infrared Sensors

Pyroelectric infrared sensors incorporating suspended zinc oxide (ZnO) pyroelectric films and thermally insulated silicon substrates are fabricated using conventional MEMS-based thin-film deposition, photolithography, and etching techniques. The responsivity of the pyroelectric films is improved through annealing at a temperature of 500 °C for 4 h. The temperature variation and voltage responsivity of the fabricated sensors are evaluated numerically and experimentally for substrate thickness in the range of 1 to 500 μm. The results show that the temperature variation and voltage responsivity both increase with a reducing substrate thickness. For the lowest film thickness of 1 μm, the sensor achieves a voltage sensitivity of 3880 mV/mW at a cutoff frequency of 400 Hz. In general, the results presented in this study provide a useful source of reference for the further development of MEMS-based pyroelectric infrared sensors.

Sensitive Planar Microwave Diode on the Base of Ternary AlxGa1-xAs Semiconductor Compound

The article presents the results of experimental studies of the dc and high-frequency electrical characteristics of planar microwave diodes that are fabricated on the base of the n-AlxGa1-xAs layer (x = 0, 0.15 or 0.3), epitaxially grown on a semi-insulating GaAs substrate. The diodes can serve as reliable and inexpensive sensors of microwave radiation in the millimeter wavelength range; they sense electromagnetic radiation directly, without any external bias voltage at room temperature. The investigation revealed a strong dependence of the detection properties of the microwave diodes on AlAs mole fraction x: in the Ka microwave frequency range, the median value of voltage responsivity is several volts per watt in the case of GaAs-based diodes (x = 0), and it substantially increases, reaching hundreds of volts per watt at higher x values. Also, a model enabling us to forecast the responsivity of the sensor in other frequency ranges is proposed.

High-responsivity graphene photodetectors integrated on silicon microring resonators

Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs’ low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10−9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print.

A Distributed Terahertz Metasurface with Cold-Electron Bolometers for Cosmology Missions

We developed and tested a 2D periodic array of cold-electron bolometers arranged into a wideband frequency selective metasurface that absorbs more than 70% of the incident power in the frequency range 100–800 GHz. The array had 10 × 10 unit cells, each containing four bolometers incorporated into a ring. The chip with bolometers was mounted on the back side of the silicon lens without a back-reflector. Preliminary experiments demonstrated voltage responsivity as high as 109 V/W for the current-biased series array. Simulation of the noise performance shows realization of background noise-limited performance with NEPtot < NEPphot for the optical power load P0 > 15 pW. Results of numerical simulation made for the unit cell of the array are presented together with the equivalent diagram based on lumped network elements. The unit cell also was developed numerically to operate in two radiation modes.

Study of Mn–Co–Ni–O thin films incorporated with Cu and Cu/Sc elements and properties of the detectors

Thin films [Formula: see text] (MCNO), [Formula: see text] (MCNCuO) and [Formula: see text] (MCNCuScO) are prepared by Chemical Solution Deposition method. The results show that the addition of Cu and Cu/Sc elements can reduce the grain boundary energy and the grain boundary angle to improve the single crystal degree of MCNO thin film. Through the analysis of MCNCuScO thin film, it is found that the stability of spinel structure mainly depends on the octahedron rather than tetrahedron. The bandgap of the samples from small to large is separately MCNCuScO, MCNCuO and MCNO films. The absorptivity within the waveband of [Formula: see text] plays a decisive role in the performance of the detector. At the same frequency, the MCNCuO thin film detector has the highest voltage responsivity, followed by the MCNCuScO thin film detector, while the MCNO film detector has the lowest responsivity.

Preload Effect Elimination Technique for Piezoelectric Force Touch Sensing in Human-Machine Interactivities

Piezoelectric touch sensing in interactive displays gains increasing attentions due to its high force detection sensitivity and intrinsic mechanical-to-electrical conversion ability. However, the instable force-voltage responsivity induced by preload effect of piezoelectric materials reduces the force detection accuracy of secondary force touches, which is important to touch and haptic applications such as peek-pop. To address this issue, in this article, we present a preload effect elimination technique, in which the relationship between the piezoelectric coefficients and static preload is studied first, and then the detected secondary force touch is calibrated by using the previously applied static force information. Experimental results demonstrate that the force detection accuracy is boosted by 15.17% after applying the developed technique to secondary force touches with different preload values, potentially allowing the system to precisely interpret secondary force touch amplitude and hence enhancing the development of touch sensing in interactive displays.

Preload Effect Elimination Technique for Piezoelectric Force Touch Sensing in Human-Machine Interactivities

Piezoelectric touch sensing in interactive displays gains increasing attentions due to its high force detection sensitivity and intrinsic mechanical-to-electrical conversion ability. However, the instable force-voltage responsivity induced by preload effect of piezoelectric materials reduces the force detection accuracy of secondary force touches, which is important to touch and haptic applications such as peek-pop. To address this issue, in this article, we present a preload effect elimination technique, in which the relationship between the piezoelectric coefficients and static preload is studied first, and then the detected secondary force touch is calibrated by using the previously applied static force information. Experimental results demonstrate that the force detection accuracy is boosted by 15.17% after applying the developed technique to secondary force touches with different preload values, potentially allowing the system to precisely interpret secondary force touch amplitude and hence enhancing the development of touch sensing in interactive displays.