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.

Impact of Methanol Concentration on Properties of Ultra-Nanocrystalline Diamond Films Grown by Hot-Filament Chemical Vapour Deposition

Diamond is a very interesting material with a wide range of properties, making it highly applicable, for example, in power electronics, chemo- and biosensors, tools’ coatings, and heaters. Due to the high demand for this innovative material based on the properties it is already expected to have, it is important to obtain homogeneous diamond layers for specific applications. Doping is often chosen to modify the properties of layers. However, there is an alternative way to achieve this goal and it is shown in this publication. The presented research results reveal that the change in methanol content during the Hot Filament Chemical Vapour Deposition (HF CVD) process is a sufficient factor to tune the properties of deposited layers. This was confirmed by analysing the properties of the obtained layers, which were determined using Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and an atomic force microscope (AFM), and the results were correlated with those of X-ray photoelectron spectroscopy (XPS). The results showed that the increasing of the concentration of methanol resulted in a slight decrease in the sp3 phase content. At the same time, the concentration of the -H, -OH, and =O groups increased with the increasing of the methanol concentration. This affirmed that by changing the content of methanol, it is possible to obtain layers with different properties.

A Review on Chemical Vapour Deposition of Two-Dimensional MoS2 Flakes

Two-dimensional (2D) materials such as graphene, transition metal dichalcogenides, and boron nitride have recently emerged as promising candidates for novel applications in sensing and for new electronic and photonic devices. Their exceptional mechanical, electronic, optical, and transport properties show peculiar differences from those of their bulk counterparts and may allow for future radical innovation breakthroughs in different applications. Control and reproducibility of synthesis are two essential, key factors required to drive the development of 2D materials, because their industrial application is directly linked to the development of a high-throughput and reliable technique to obtain 2D layers of different materials on large area substrates. Among various methods, chemical vapour deposition is considered an excellent candidate for this goal thanks to its simplicity, widespread use, and compatibility with other processes used to deposit other semiconductors. In this review, we explore the chemical vapour deposition of MoS2, considered one of the most promising and successful transition metal dichalcogenides. We summarize the basics of the synthesis procedure, discussing in depth: (i) the different substrates used for its deposition, (ii) precursors (solid, liquid, gaseous) available, and (iii) different types of promoters that favour the growth of two-dimensional layers. We also present a comprehensive analysis of the status of the research on the growth mechanisms of the flakes.

Self-consistent modeling of microwave activated N2/CH4/H2 (and N2/H2) plasmas relevant to diamond chemical vapour deposition

The growth rate of diamond by chemical vapour deposition (CVD) from microwave (MW) plasma activated CH4/H2 gas mixtures can be significantly enhanced by adding trace quantities of N2 to the process gas mixture. Reasons for this increase remain unclear. The present article reports new, self-consistent two-dimensional modelling of MW activated N2/H2 and N2/CH4/H2 plasmas operating at pressures and powers relevant to contemporary diamond CVD, the results of which are compared and tensioned against available experimental data. The enhanced N/C/H plasma chemical modelling reveals the very limited reactivity of N2 under typical processing conditions and the dominance of N atoms amongst the dilute ‘soup’ of potentially reactive N-containing species incident on the growing diamond surface. Ways in which these various N-containing species may enhance growth rates are also discussed.