To realize high-resolution thermal images with high quality, it is essential to improve the noise characteristics of the widely adopted uncooled microbolometers. In this work, we applied the post-metal annealing (PMA) process under the condition of deuterium forming gas, at 10 atm and 300 °C for 30 min, to reduce the noise level of amorphous-Si microbolometers. Here, the DC and temperature coefficient of resistance (TCR) measurements of the devices as well as 1/f noise analysis were performed before and after the PMA treatment, while changing the width of the resistance layer of the microbolometers with 35 μm or 12 μm pixel. As a result, the microbolometers treated by the PMA process show the decrease in resistance by about 60% and the increase in TCR value up to 48.2% at 10 Hz, as compared to the reference device. Moreover, it is observed that the noise characteristics are improved in inverse proportion to the width of the resistance layer. This improvement is attributed to the cured poly-silicon grain boundary through the hydrogen passivation by heat and deuterium atoms applied during the PMA, which leads to the uniform current path inside the pixel.

To realize the chip-scale atomic clocks (CSACs) for atomic reference with miniaturization and low power consumption, there are technological challenges in the physics package for compact and stable frequency standards. Here, the precise thermal management and the exact magnetic-field control of the physics package are required for accurate clocks. Also, high thermal resistance for the physics package helps to considerably reduce power consumption of the CSAC. Thus, in this study, a compact physics package with embedded magnetic shielding has been developed by using flexible hybrid approach for a chip-scale atomic clock. The vertical-cavity surface-emitting laser (VCSEL) and the MEMS hotplate on a flexible circuit board (FPCB) are vertically stacked and bound with a QWP and a MEMS vapor cell by aluminum foil. The aluminum bound structure is suspended by the polyimide core of the FPCB for high thermal resistance. Also, the mu-metal fixture is applied for magnetic shield and FPCB suspension, while the MEMS hotplate with a resistance heater and an amorphous Si based thermistor is adopted for thermal management of the physics package. Then, the planar integrated FPCB is folded and stacked vertically at an intersection with the mu-metal fixture. As a result, the CSAC incorporating the proposed physics package reveals the CPT linewidth of 5.6 kHz and low power consumption of about 200mW. The measured frequency short-term stability is about 5.2×10-12 τ-1/2 at 1000-second integration. The observed results demonstrate promising performances of the flexible hybrid physics package for its use in miniaturized atomic clocks.

High crystalline ZnO nanorods (NRs) on Zn pre-deposited graphene/Cu sheet without graphene transfer process have been fabricated by self-catalyzed vapor-phase transport synthesis. Here, the pre-deposited Zn metal on graphene not only serves as a seed to grow the ZnO NRs, but also passivates the graphene underneath. The temperature-dependent photoluminescence spectra of the fabricated ZnO NRs reveal a dominant peak of 3.88 eV at 10 K associated with the neutral-donor bound exciton, while the redshifted peak by bandgap shrinkage with temperature and electron-lattice interactions leads a strong emission at 382 nm at room temperature. The optical absorption of the ZnO NRs/graphene hetero-nanostructure at this ultraviolet (UV) emission is then theoretically analyzed to quantify the absorption amount depending on the ZnO NR distribution. By simply covering the ZnO NR/graphene/Cu structure with the graphene/glass as a top electrode, it is observed that the current-voltage characteristic of the ZnO NR/graphene hetero-nanojunction device exhibits a photocurrent of 1.03 mA at 3 V under a light illumination of 100 μW/cm². In particular, the suggested graphene/ZnO NRs/graphene hybrid-nanostructure-based devices reveal comparable photocurrents at a bidirectional bias, which can be a promising platform to integrate 1D and 2D nanomaterials without complex patterning process for UV device applications.

A graphene-InGaN Schottky junction has been successfully fabricated by transferring graphene layers onto n-type In _0.23 Ga _0.77 N/GaN/Al ₂ O ₃ substrates.