Molybdenum disulfide (MoS2) is a cutting-edge layer-dependent two dimensional semiconductor which monolayer is direct-bandgap. Nano-scale monolayer MoS2 has big potential in electronics and optoelectronics devices. In this work we reported the progress in growing continuous single layer MoS2 by ambient pressure chemical vapor deposition (APCVD). Scanning electron microscope (SEM), Raman, photoluminescence spectra (PL) and atomic force microscopy (AFM) disclose that as-grown films are large-area monolayer and of high quality. SEM observations also clearly reveal the growth process of these films. Figuring out the growth mechanism grants growth of large scale continuous MoS2, and lays the foundation for wide device applications in the future.

Recently, great efforts have been devoted to study of molybdenum disulfide (MoS2), particularly monolayer MoS2 semiconductor thin films, due to its excellent electrical and optical properties. Direct growth of continuous monolayer MoS2 films by ambient-pressure chemical vapor deposition is reported herein. Optical microscopy, Raman spectroscopy, photoluminescence spectra (PL), atomic force microscopy, x-ray photoelectron spectroscopy (XPS), and high-resolution transmission electronic microscopy were used to characterize the electronic and structural properties of the films, demonstrating that the MoS2 films grown on silicon dioxide/silicon (SiO2/Si) substrate with spatial size on micron scale were high quality, single crystal, continuous, and monolayer. Raman and PL mapping were performed to confirm the uniformity of the monolayer MoS2 films. The morphological variation of the MoS2 films after different reaction times was observed by optical microscopy and scanning electron microscopy, revealing the growth process and thus helping to understand that the growth mechanism during synthesis of continuous large-area films depends on the distribution of the reactive intermediate molybdenum oxide (MoO3−x) due to its lower saturation vapor density. Back-gated transistors based on MoS2 films were fabricated, exhibiting current on/off ratio of ∼ 104 and subthreshold swing (SS) of 0.44 V dec−1. This work contributes to synthesis of large-area continuous films, thus paving the way for future scaled-up fabrication of MoS2 electronic devices.

The monolayer MoS2 thin film was deposited directly on quartz substrate by chemical vapor deposition (CVD) approach using MoO3 and sulfur powders as reactants.The surface morphology of the grown films was observed by metallographic optical microscope,scanning electron microscope (SEM) and atomic force microscopy (AFM).The grown MoS2 films turn to be layered-nano structure.Raman spectroscopic and photoluminescence (PL) spectroscopic analyses were conducted to evaluate the structural and optical property of the grown MoS2 nano films.The results show the presence of single,double and triple MoS2 films on the quartz substrate.Apart from this,photoluminescence phenomenon was observed on single,double and triple MoS2 films.Besides,the band structure change of MoS2 film then it turns from bulk to single layer film is theoretically analyzed,which is consistent with our experimental results.

Silicon-rich silicon nitride (SRSN) films with different excess of silicon were prepared by plasma enhanced chemical vapor deposition (PECVD). Amorphous silicon quantum dots (Si QDs) were in-situ synthesized without annealing, while crystalline Si QDs were formed after 1100 degrees C annealing. The mechanisms of photoluminescence (PL) emission of samples annealed at different temperatures were investigated. The PL emission of the as-deposited samples shows little change while that of the annealed samples at 1100 degrees C exhibits an obvious redshift with the increase of excitation wavelength from 325 nm to 532 nm. The quantum confinement effect (QCE) in Si QDs was found to dominant the PL emission of all the as-deposited samples and the samples annealed at 1100 degrees C. In addition, excitation energy-induced QD size selection was also found to play a significant role in the 1100 degrees C annealed samples with inhomogeneous size distribution of Si QDs. (C) 2015 Elsevier Ltd. All rights reserved.

An Ag/TCO tandem film are used as front electrode of thin film solar cells, which are composed of super thin Ag film and a textured thin TCO film. This Ag/TCO tandem film has the advantage of high transparency and high conductivity of super thin Ag film. Meanwhile, it solved the laser scribing problems when use Ag film as front electrode in the industry manufacturing processes of thin film solar cells. In experimental, 9 glasses with different thickness SnO2:F film on it are deposited 3/, optical transparent 89%, thickness in 10-15nm super thin Ag film with DC magnet sputtering technology. And these samples are manufactured as a-Si thin film solar panels in same processes. The result shows that when the SnO2:F film have a 80/ sheet resistance it could get the best performance in a-Si solar cells with 4% increase in output power than traditional a-Si solar cells.

The microstructure evolution of Si-rich amorphous a-SiC:H films obtained under different annealing conditions was investigated by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The influence of its microstructure on the energy band alignment at a Si-rich a-SiC:H/n-type c-Si hetero-interface was analyzed by ultraviolet visible transmission spectroscopy and ultraviolet photoelectron spectroscopy. The results revealed that the as-deposited Si-rich a-SiC:H film was mainly in an amorphous state. After annealing, Si and SiC quantum dots (QDs) formed, and the crystallinity of the QDs and the proportion of SiC QDs increased with increasing the annealing time at the same annealing temperature. It is found that the energy band alignment at the hetero-interface was influenced by the crystallinity of the films, the sizes of the QDs, and the relative proportion of Si to SiC QDs in a-SiC:H films. Moreover, the contact potential at the hetero-interface decreased with the improved crystallinity of the QDs in a-SiC:H film. The determination of energy band alignment at the Si-rich a-SiC:H/c-Si hetero-interface is beneficial to understanding the carrier transport behavior and designing hetero-structure devices.