Oxide semiconductors are desirable for large-area and/or flexible electronics. Here, we report highly optimised complementary inverters based on n-type indium gallium zinc oxide and p-type tin monoxide thin-film transistors. Oxide-based inverters with a record voltage gain of 142 have been achieved. The switching point voltage has also been tuned to reach the ideal value, namely half value of the supply voltage. A narrow transition width of 1.04 V (13% of the supply voltage) is achieved which offers a strong anti-jamming ability to avoid logic errors. Rail-to-rail output voltage swing has been achieved. The inverters still maintain high performance at a low supply voltage of 6 V. A very large number of inverters have been fabricated and showed excellent uniformity in a working area of 1 cm × 1 cm. The switching point voltage and transition width show very small standard deviations of only 0.55% (0.022 V) and 2.3% (0.024 V), respectively, demonstrating promises for large-scale circuit integration.

We present a system for sensing and reconstructing facial expressions of the virtual reality (VR) head-mounted display (HMD) user. The HMD occludes a large portion of the user's face, which makes most existing facial performance capturing techniques intractable. To tackle this problem, a novel hardware solution with electromyography (EMG) sensors being attached to the headset frame is applied to track facial muscle movements. For realistic facial expression recovery, we first reconstruct the user's 3D face from a single image and generate the personalized blendshapes associated with seven facial action units (AUs) on the most emotionally salient facial parts (ESFPs). We then utilize preprocessed EMG signals for measuring activations of AU-coded facial expressions to drive pre-built personalized blendshapes. Since facial expressions appear as important nonverbal cues of the subject's internal emotional states, we further investigate the relationship between six basic emotions -anger, disgust, fear, happiness, sadness and surprise, and detected AUs using a fern classifier. Experiments show the proposed system can accurately sense and reconstruct high-fidelity common facial expressions while providing useful information regarding the emotional state of the HMD user.

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Oxide semiconductors are ideal candidates for flexible and transparent electronics. Here, we report complementary inverters based on p-type tin monoxide and n-type indium-gallium-zinc-oxide thin-film transistors. The inverters have a gain of 63 at a supply voltage, VDD, of 1.5 V with a maximum static power consumption of 15.6 nW, and a gain of 226 at a VDD of 3.0 V with a maximum power consumption of 241.2 nW. A five-stage ring oscillator (RO) based on the complementary inverters are able to operate at 1.04 kHz, with full amplitude oscillations at a VDD of 1.5 V. All the inverters and RO are fabricated on silicon wafers but at a maximum processing temperature of 225 o C, so that the results are relevant to possible flexible applications. The extremely low power consumption of nanowatt, high gain, kHz operation, and possible flexibility of the fabricated complementary components are well suited to meet the requirements of wearable electronics, internet of things technology, etc. Index Terms-Complementary inverter, indium gallium zinc oxide (InGaZnO or IGZO), tin monoxide (SnO), low-power, high gain, ring oscillator (RO), thin-film transistor (TFT).