Top-gate field-effect transistor based on monolayer WS2 with an ion-gel gate dielectric

A top-gate field-effect transistor (FET), based on monolayer (ML) tungsten disulfide (WS2), and with an ion-gel dielectric was developed. The high electrical contact resistance of the Schottky contacts at the n-type transition metal dichalcogenides/metal electrode interfaces often adversely affects the device performance. We report the contact resistance and Schottky barrier height of an FET with Au electrodes. The FET is based on ML WS2 that was synthesised using chemical vapour deposition and was assessed using the transfer-length method and low-temperature measurements. Raman and photoluminescence spectra were recorded to determine the optical properties of the WS2 layers. The ML WS2 FET with an ion-gel top gate dielectric exhibits n-type behaviour, with a mobility, on/off ratio of 1.97 cm2/V·s, 1.51×105, respectively.

Thermal Qualification of the UHTCMCs Produced Using RF-CVI Technique with VMK Facility at DLR

Ultra high-temperature ceramic matrix composites (UHTCMCs) based on carbon fibre (Cf) have been shown to offer excellent temperature stability exceeding 2000 °C in highly corrosive environments, which are prime requirements for various aerospace applications. In C3Harme, a recent European Union-funded Horizon 2020 project, an experimental campaign has been carried out to assess and screen a range of UHTCMC materials for near-zero ablation rocket nozzle and thermal protection systems. Samples with ZrB2-impregnated pyrolytic carbon matrices and 2.5D woven continuous carbon fibre preforms, produced by slurry impregnation and radio frequency aided chemical vapour infiltration (RF-CVI), were tested using the vertical free jet facility at DLR, Cologne using solid propellants. When compared to standard CVI, RFCVI accelerates pyrolytic carbon densification, resulting in a much shorter manufacturing time. The samples survived the initial thermal shock and subsequent surface temperatures of >2000 °C with a minimal ablation rate. Post-test characterisation revealed a correlation between surface temperature and an accelerated catalytic activity, which lead to an understanding of the crucial role of preserving the bulk of the sample.

Microstructural Analysis of Copper Foil Etched and Annealed in ECR Plasma Reactor

Microstructural analysis of commercially available cold-rolled polycrystalline copper foil, etched and annealed in an in-house developed Electron Cyclotron Resonance (ECR) Plasma Enhanced Chemical Vapour Deposition (PE-CVD) reactor, have been carried out using x-ray diffraction (XRD) studies. The annealing experiments were carried out under a vacuum environment, keeping the working pressure of the reactor at 50×10-3 mbar, for three different time spans of 30 mins, 45 mins and 1 hour at 823 K (550 °C) and 923 K (650 °C) respectively in presence of hydrogen plasma. The XRD studies reveal the significance of annealing time at two different temperatures for the determination of physical and microstructural parameters such as the average grain size and micro-strain in copper lattice by Williamson-Hall (W-H) method.

Изучение многополосного экситонного спектра ZnSe в области 477-490 нм

Изучены спектры фотолюминесценции поликристаллического CVD (chemical vapour deposition) ZnSe, выращенного с большим избытком селена и содержащего комплексы \O*Se-Cu+i\ на дефектах упаковки. Измерено поглощение, дополняющее эти данные. Рассмотрены особенности спектров фотолюминесценции по сравнению с катодолюминесценцией. Показано, что идентичные полосы фотолюминесценции наблюдаются как несколько более коротковолновые, чем полосы катодолюминесценции. Для исследованных кристаллов представлена зонная модель согласно результатам, полученным в данной работе. Длинноволновое смещение спектров фотолюминесценции при уменьшении энергии возбуждения соответствует сдвигу по энергетической шкале зонной модели с соответствующим изменением типа излучательных переходов. Внесены изменения, определяющие природу группы эквидистантных полос 477-490 нм, характерных для образцов ZnSe с избытком кислорода и Se. Результаты могут быть полезны для более полного изучения структуры многофононных экситонных спектров фото- и катодолюминесценции кристаллов АIIВVI. Ключевые слова: зонная модель, узколинейчатые многофононные спектры, экситонное излучение, дефекты упаковки, изоэлектронная примесь кислорода, несущая эффективный отрицательный заряд.

Correction: Synthesis of pyrite thin films and transition metal doped pyrite thin films by aerosol-assisted chemical vapour deposition

Correction for ‘Synthesis of pyrite thin films and transition metal doped pyrite thin films by aerosol-assisted chemical vapour deposition’ by Sadia Khalid et al., New J. Chem., 2015, 39, 1013–1021, DOI: 10.1039/C4NJ01461H.

Fabrication of graphene–ZnO heterostructure-based flexible and thin platform-based UV detector

This work presents the performance evaluation of Graphene/ZnO Schottky junctions grown on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates. The fabricated structures include chemical vapour deposition grown graphene layer on ITO-coated PET substrates. Polymethyl methacrylate assisted transfer method has been employed for the successful transfer of graphene from Cu substrate to PET. The smaller D-band intensity (1350 cm−1) compared to G-band (1580 cm−1) indicates good quality of carbon lattice with less number of defects. High-quality ZnO has been deposited through RF sputtering. The deposited ZnO with grain size 50–95 nm exhibited dislocation densities of 1.31270 × 10–3 nm−2 and compressive nature with negative strain of − 1.43156 GPa. Further, the electrical and optical characterization of the devices has been done through device I–V characterization and UV detection analysis. The UV detection capability of the device has been carried out with the aid of a UV-lamp of 365 nm wavelength. The fabricated graphene/ZnO photodetector showed good response to UV illumination. The device performance analysis has been done through a comparison of the device responsivity and detectivity with the existing detectors. The detectivity and responsivity of the fabricated detectors were 7.106 × 109 mHz1/2 W−1 and 0.49 A W−1, respectively.