MoS2 nanoparticle formation in a low pressure environment

Formation of MoS2 nanoparticles at pressures between 0.5 and 10 Torr has been studied. Two different chemistries for the particle nucleation are compared: one based on MoCl5 and H2S, and the other based on MoCl5 and S. In both cases particle formation has been studied in a thermal oven and in a radio-frequency discharge. Typically, the reaction rates at low pressures are too low for an efficient thermal particle production. At pressures below 10 Torr no particle production in the oven is achieved in H2S chemistry. In the more reactive chemistry based on sulfur, the optimal conditions for thermal particle growth are found at 10 Torr and low gas flows, using excess of hydrogen. In the radio-frequency discharge, nanoparticles are readily formed in both chemistries at 0.5 Torr and can be detected in situ by laser light scattering. In the H2S chemistry particles smaller than 100 nm diameter have been synthesized, the sulfur chemistry yields somewhat larger grains. Both in thermal and plasma-enhanced particle syntheses, using excess of hydrogen is beneficial for the stability and purity of the particles

Energy influx from an rf plasma to a substrate during plasma processing

The energy influx delivered by an rf plasma to a metal substrate has been studied by a calorimetric method with a thermal probe. By changing the substrate voltage, the influence of the kinetic energy of the charge carriers to the thermal power could be determined. The measured energy influx for an argon plasma can be explained mainly by ions, electrons, and their recombination. In the case of an oxygen plasma, where the energy influx is under comparable conditions about 50% higher, also other transfer mechanisms such as surface-aided atom association and relaxation of rovibrational states have to be taken into consideration

Finite element analysis of thermo-elastical modal damping of mems vibrations

The paper deals with finite element analysis of damped modal vibrations Q-factor values determined by thermal-elastic damping in micro-electrical-mechanical systems (MEMS). Mathematically the problem is formulated as a complex eigenvalue problem. Verification problems have been solved by using several computational environments and different presentations of model equations in order to comprehend and reduce the influence of rounding errors. The analysis of damped modal properties of selected real MEMS resonator revealed the main features of thermal-elastic damping by taking into account 3D geometry of the resonator and anchoring (clamping) structur

Combined identification and prediction algorithms

Рассматривается задача построения математической модели зависимости выходных переменных от входных переменных стохастического объекта с учетом априорных знаний о зависимости. Для решения этой проблемы используются как параметрические, так и непараметрические подходы. В работе предлагаются комбинированные алгоритмы идентификации и прогнозирования стохастических объектов с использованием линейной комбинации непараметрических и параметрических оценок регрессии

Analysis of threshold voltage instabilities in semi-vertical GaN-on-Si FETs

We present a first study of threshold voltage instabilities of semi-vertical GaN-on-Si trench-MOSFETs, based on double pulsed, threshold voltage transient, and UV-Assisted C-V analysis. Under positive gate stress, small negative V th shifts (low stress) and a positive V thshifts (high stress) are observed, ascribed to trapping within the insulator and at the metal/insulator interface. Trapping effects are eliminated through exposure to UV light; wavelength-dependent analysis extracts the threshold de-Trapping energy ≈2.95 eV. UV-Assisted CV measurements describe the distribution of states at the GaN/Al2O3 interface. The described methodology provides an understanding and assessment of trapping mechanisms in vertical GaN transistors