We present a practical vacuum pressure sensor based on the Schottky junction using graphene anchored on a vertically aligned zinc oxide nanorod (ZnO-NR). The constructed heterosystem of the Schottky junction showed characteristic rectifying behavior with a Schottky barrier height of 0.64 eV. The current–voltage (I–V) features of the Schottky junction were measured under various pressures between 1.0 × 103 and 1.0 × 10− 3 mbar. The maximum current of 38.17 mA for the Schottky junction was measured at – 4 V under 1.0 × 10− 3 mbar. The high current responses are larger than those of the previously reported vacuum pressure sensors based on ZnO nanobelt film, ZnO nanowires, and vertically aligned ZnO nanorod devices. The pressure-sensitive current increases with the vacuum pressure and reaches maximum sensitivity (78.76%) at 1.0 × 10− 3 mbar. The sensitivity and repeatability of the Schottky junction were studied by the current–time (I–T) behavior under variation of vacuum pressure. The sensing mechanism is debated from the surface charge transfer doping effect by oxygen chemisorption. The results suggest that this simple graphene/ZnO-NR Schottky junction device may have potential in the fabrication of vacuum pressure sensor with high sensitivity.

Metal foam has many excellent properties, such as light weight, incombustibility, good thermal insulation, sound absorption, energy absorption, and environmental friendliness. It has two types of macrostructure, a closed-cell foam with sealed pores and an open-cell foam with open pores. The open-cell foam has a complex macrostructure consisting of an interconnected network. It can be exploited as a degradable biomaterial and a heat exchanger material. In this paper, open cell Mg alloy foams have been produced by infiltrating molten Mg alloy into porous pre-forms, where granules facilitate porous material. The granules have suitable strength and excellent thermal stability. They are also inexpensive and easily move out from open-cell foamed Mg-Al alloy materials. When the melt casting process used an inert gas, the molten magnesium igniting is resolved easily. The effects of the preheating temperature of the filler particle mould, negative pressure, and granule size on the fluidity of the open cell Mg alloy foam were investigated. With the increased infiltration pressure, preheat temperature and granule sizes during casting process, the molten AZ31 alloy was high fluidity. The optimum casting temperature, preheating temperature of the filler particle mould, and negative pressure were 750˚C, 400-500˚C, and 5000-6000 Pa, respectively, At these conditions the AZ31 alloy had good fluidity and castability with the longest infiltration length, fewer defects, and a uniform pore structure.

This study investigates GaAs dry etching in capacitively coupled BCl3/N2 plasma at a low vacuum pressure (>100 mTorr). The applied etch process parameters were a RIE chuck power ranging from 100~200W on the electrodes and a N2 composition ranging from 0~100% in BCl3/N2 plasma mixtures. After the etch process, the etch rates, RMS roughness and etch selectivity of the GaAs over a photoresist was investigated. Surface profilometry and field emission-scanning electron microscopy were used to analyze the etch characteristics of the GaAs substrate. It was found that the highest etch rate of GaAs was 0.4μm/min at a 20 % N2 composition in BCl3/N2 (i.e., 16 sccm BCl3/4 sccm N2). It was also noted that the etch rate of GaAs was 0.22μm/min at 20 sccm BCl3 (100 % BCl3). Therefore, there was a clear catalytic effect of N2 during the BCl3/N2 plasma etching process. The RMS roughness of GaAs after etching was very low (~3nm) when the percentage of N2 was 20 %. However, the surface roughness became rougher with higher percentages of N2.

This study investigated dry etching of acrylic in capacitively coupled SF6, SF6/O2 and SF6/CH4 plasma under a low vacuum pressure. The process pressure was 100 mTorr and the total gas flow rate was fixed at 10 sccm. The process variables were the RIE chuck power and the plasma gas composition. The RIE chuck power varied in the range of 25~150 W. SF6/O2 plasma produced higher etch rates of acrylic than pure SF6 and O2 at a fixed total flow rate. 5 sccm SF6/5 sccm O2 provided 0.11μm/min and 1.16μm/min at 25W and 150W RIE of chuck power, respectively. The results were nearly 2.9 times higher compared to those at pure SF6 plasma etching. Additionally, mixed plasma of SF6/CH4 reduced the etch rate of acrylic. 5 sccm SF6/5 sccm CH4 plasma resulted in 0.02μm/min and 0.07μm/min at 25W and 150W RIE of chuck power. The etch selectivity of acrylic to photoresist was higher in SF6/O2 plasma than in pure SF6 or SF6/CH4 plasma. The maximum RMS roughness (7.6 nm) of an etched acrylic surface was found to be 50% O2 in SF6/O2 plasma. Besides the process regime, the RMS roughness of acrylic was approximately 3~4 nm at different percentages of O2 with a chuck power of 100W RIE in SF6/O2 plasma etching.