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PtTe 2 and PtSe 2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer (ML) film has been reported for PtSe 2 , so far the evolution of electronic structure of atomically thin PtTe 2 films still remains unexplored. Here we report a systematic angleresolved photoemission spectroscopy (ARPES) study of the electronic structure of high quality PtTe 2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML. ARPES measurements show that PtTe 2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe 2 film. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4-6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe 2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe 2 films. Our work reveals the transition from 2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.

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A metal-oxide-semiconductor structure with NiSi2 nanocrystals embedded in the SiO2 layer has been fabricated. A pronounced capacitance-voltage hysteresis was observed with a memory window of 1 V under the 2 V programming voltage. The processing of the structure is compatible with the current manufacturing technology of semiconductor industry.

Trifluoromethane-containing plasma is used to passivate the mesa surfaces and suppresses the surface leakage current of GaN p-i-n rectifiers. Reduction of surface leakage enhances the reverse blocking voltage by 25% measured at J = 1 A/cm 2 . Differential forward resistances of control samples and plasma-treated ones are 0.65 and 0.49 m -cm 2 , respectively, and an excellent Baliga's figure-of-merit of more than 800 MW/cm 2 , as compared with the conventional 545 MW/cm 2 , is achieved for GaN diodes fabricated on sapphire substrates.

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The impact of aluminum (Al) implantation into TiN/HfO 2 /SiO 2 on the effective work function is investigated. Al implanted through poly-Si cannot attain sufficient flatband voltage (V FB ) shift unless at higher implantation energy. Al implanted through TiN at 1.2 keV with a dose of 5 × 10 15 cm −2 raised the V FB to about 250 mV compared with a nonimplanted gate stack. Moreover, the V FB shift can be up to about 800 mV at 2 keV with the same dose level accompanied with slightly equivalent oxide thickness penalty and gate leakage current degradation. Optimized process window to control Al diffusion depth was essential to minimize these impacts.Index Terms-Al Implant, effective work function (EWF), HfO 2 .

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