Chemical Vapor Deposition最新文献

In this article, three novel cyclopentadienyl precursors are evaluated for the atomic layer deposition (ALD) of erbium oxide, with either ozone or water as the oxygen source. The erbium precursors evaluated are Er(ⁱPrCp)₃, Er(MeCp)₂(ⁱPr-amd), and Er(ⁿBuCp)₃. The films are deposited on silicon within the temperature range 200–400°C. Self-limiting growth is achieved with all three precursors, with both ozone and water. It is found that the water processes of all three precursors present significantly higher growth rates when compared to the ozone processes. An up to three-fold increase in the growth rate is observed for the water processes of Er(ⁱPrCp)₃ and Er(MeCp)₂(ⁱPr-amd) (amd: amidinate) when compared to their ozone processes. The films are smooth and uniform, as determined by atomic force microscopy (AFM) (rms roughness < 3% of film thickness). The composition of the films is investigated by means of X-ray photoelectron spectroscopy (XPS). It is found that the films contain small amounts of carbon as an impurity, especially in the case of ozone-processed films. Using Er(ⁿBuCp)₃ together with ozone as the oxygen source, a highly conformal Er₂O₃ thin film is deposited on a 1:60 high-aspect-ratio substrate. This is the first report of the conformal growth of Er₂O₃ thin films by ALD on a high-aspect-ratio structure.

We report on a simple and effective method of synthesizing graphene-like nanosheets on silicon substrates pre-deposited with a carbon film or carbon nanodots in hot-filament(HF)CVD from a methane precursor. The results of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and micro-Raman spectroscopy (RS) indicate that the structure of graphene-like nanosheets is changed with the flow rate change of methane and the pretreatment of the substrate surface. The catalyst-free growth of graphene-like nanosheets is related to the diffusion and assembly of carbon atoms on the substrate surface and the separation of graphene-like nanosheets from the substrate surface.

Recently, enormous interest has been focused on the nanofabrication of optical micro- and nanocavities for applications in lab-on-a-chip and quantum optics. At the same time, the atomic layer deposition (ALD) process presents several advantages for the fabrication and modification of micro- and nanostructures because of its atomic level thickness fine-tuning and perfect coating conformability in three-dimensional (3D) structures. Hence, ALD technology has been directed into the field of optical microcavities for the tracking and tuning of their properties. In this short review, we will summarize recent progress in the application of ALD on optical microcavities. Firstly, we will briefly introduce ALD technology and emphasize its distinctive features when applied to optical microcavities. Then, various microcavities such as photonic crystals, opals, and tubular microcavities will be illustrated to demonstrate their development with the assistance of ALD technology. Such an influential manufacturing tool for optical devices could inspire numerous interesting applications, as concluded in the final part.

A novel approach for functional thin film deposition using laser flash evaporation as the precursor delivery system is reported. In this newly established CO₂-laser-assisted (LA)CVD, solid precursors with low volatility are non-selectively sublimated by absorption of infrared laser radiation. Thus, the method allows for the highly controlled growth of multicomponent thin films with desired composition and stoichiometry over the entire growth period. Thin film microstructural features, such as the morphology, density, and thickness of the films can be adjusted by tuning the process parameters. These features, characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy (RS), are discussed for LiCoO₂ thin films. Additional analyses include X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES), cyclic voltammetry (CV), and galvanostatic cycling.

Metallic copper thin layers are deposited by means of a modified metal-organic (MO)CVD method via passing formic acid vapor through a finely dispersed powder of a solid metal-containing reactant (Cu/CuO) under thermal and plasma activation. To characterize the copper layers obtained, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and UV-vis spectroscopy, scanning electron microscopy (SEM), diffraction of synchrotron radiation (DSR) analyses, and laser interferometry, are used. The layers are found to be crystalline with a nanometer-scale grain structure, the parameters of which depend on the experimental conditions and chemical composition, with a predominant content of copper in the metallic state, Cu⁰. It is revealed that the plasma activation causes a decrease in the mean size of copper grains, as well as film thickness. Average growth rates inherent in the films obtained under thermal and plasma conditions are calculated. Based on studying the composition of a gas-phase copper complex synthesized, a schematic diagram of chemical conversion is suggested for the combined synthesis-transport process (CST).

Pt supported on mesoporous silica SBA-15 materials with various loadings are controllably synthesized by metal-organic(MO)CVD of Pt(C₅H₉)₂ in a Y-tube reactor. The precursor, Pt(C₅H₉)₂, is successfully prepared by the reaction of dichloro(1,5-cyclooctadiene)platinum ((COD)PtCl₂) with pent-4-en-1-ylmagnesium bromide, which is confirmed by proton nuclear magnetic resonance (¹H-NMR). Transmission electron microscopy (TEM) images show that Pt nanoparticles with an average size of 4.6 ± 1.1 nm are dispersed uniformly onto the SBA-15. The performance of Pt/SBA-15 for the hydrogenation of o-chloronitrobenzene (o-CNB) is tested, and is able to achieve high catalytic activity (97%) and selectivity (72%).

Pulsed plasma-enhanced (PE)CVD is used for the growth of vertically aligned multiwall carbon nanotubes (CNTs) at a low temperature range of 350–490 °C. A pulsed plasma is generated by the application of a rectangular negative pulse to the substrate electrode with an on time of 4.5 μs, off time of 5.5 μs, duty cycle of 45%, and pulse repetition frequency of 100 kHz. CNTs are synthesized from Ni catalyst film of 20–40 nm thickness deposited on a silicon substrate under pressures of 0.01 and 0.5 Torr by magnetron sputtering. The effect of Ni catalyst film morphology on low temperature growth of CNTs by pulsed PECVD is studied. It is found that CNTs grown from Ni catalyst films depend on the process pressure employed to prepare the film by magnetron sputtering. A comparison with the direct current (DC) discharge-produced CNTs reveals that the growth rate of pulsed plasma-produced CNTs is two times higher. CH species density is studied using optical emission spectroscopy (OES) by an actinometrical approach, which shows that DC discharge plasma has a higher CH concentration, but still has a lower growth rate. Further, it is observed that using pulsed plasma, growth of CNTs is possible at temperatures down to 350 °C, whereas in the case of DC discharge plasma, CNTs growth is possible only at temperatures down to 450 °C in the present experimental set-up. Possible reasons for the better performance of pulsed plasma in respect of growth rate and low temperature growth are discussed.