Effect of diluent gas on silicon film deposition from a free jet of monosilane-diluent mixture activated by electron-beam plasma

Зайковский

et al. 2016

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Nanowires of silicon oxide SiOx (x ≤ 2) were synthesized from a mixture of monosilane and hydrogen (helium, argon) by gas‐jet electron beam plasma chemical vapor deposition (GJ EBP CVD) method with simultaneous supply of oxygen into the vacuum chamber. The synthesis was performed on monocrystalline silicon and glass substrates coated with micron‐sized particles of a tin catalyst. In particular, aligned arrays of nanowire bundles (microropes) were synthesized from a mixture of monosilane and hydrogen (argon). A bundle of amorphous silicon oxide nanowires, each of which is about 15 nm in diameter, grows from a catalyst particle. The growth rate of the microropes is about 25 nm s−1 at a synthesis temperature of 320–330 °C. The morphology of the nanostructures was investigated by transmission and scanning electron microscopy, their composition by X‐ray energy dispersive spectroscopy and optical properties by photoluminescence spectroscopy. The synthesis was carried out using the well‐known vapor–liquid–solid (VLS) mechanism. A model is proposed for the synthesis of the nanostructures by the above method, including the formation of aligned bundles of nanowires (microropes) due to nonuniform heating of the catalyst particle by directed plasma flow. The obtained nanostructures have intense photoluminescence in the visible region of the spectrum at room temperature.

Section: Resultsmentioning

confidence: 99%

Synthesis of silicon oxide nanowires by the GJ EBP CVD method using different diluent gases

Зайковский

et al. 2016

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Section: Methodsmentioning

confidence: 99%

“…Previously, the gas‐jet electron beam plasma chemical vapor deposition method has been used to deposit silicon and silicon suboxide films and grow silicon oxide nanowires . A description of the method can be found in . Silicon oxide nanowires were synthesized as follows: a substrate with a catalyst film was heated to the working temperature and then treated with hydrogen plasma, after which monosilane was added to hydrogen to directly grow nanostructures.…”

Section: Methodsmentioning

confidence: 99%

Influence of substrate temperature on the morphology of silicon oxide nanowires synthesized using a tin catalyst

Zamchiy

et al. 2016

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Silicon oxide nanowires SiOx were synthesized by the gas‐jet electron beam plasma chemical vapor deposition method. The synthesis of nanostructures was carried out on silicon substrates with thin tin film as a catalyst. The evolution in the morphology of the obtained structures was investigated while changing the substrate temperature in the range 200–415 °C. Dense array of aligned nanowire bundles (microropes) is formed at a temperatures of 335 and 415 °C. With decrease in the temperature to 270 and 245 °C arrays of microropes transform into cocoon‐like structures of nanowires. At a temperature 200 °С, array formed almost entirely consisting of cocoon‐like structures. The results of X‐ray energy dispersive spectroscopy (EDS) of the nanowires show that the ratio of oxygen to silicon is on average Si:O = 1:2.4. At the same time, Fourier Transform Infrared spectroscopy (FTIR) analysis of the obtained nanostructures showed that the synthesized nanowires consist of SiOx with x around 2. Moreover, the composition of the structures remains practically unchanged with the variation of the substrate temperature. The IR spectra show bands due to both Si–OH bonds and water molecules. Measurements of contact angles for water showed that the nanowire film surface synthesized in this work is hydrophilic in nature. When structuring involves the oriented growth microropes, the contact angle is about 20–35°. Decreasing of the substrate temperature and formation of cocoon‐like structures leads to a decrease in the contact angle to 4–12°. The photoluminescence (PL) spectra of nanostructures synthesized at the different substrate temperatures consist of a broad band with a maximum around 2.5 eV when using laser at 325 nm as the exciting source. We assume that the composition of the nanowires is close to SiO2, and the excess of oxygen in structures composition is due to the influence of adsorbed water molecules and hydroxyl groups with the formation of Si–OH bonds. Apparently, these bonds define the photoluminescence spectrum.

“…Thus, increasing the argon flow rate in the reactant mixture leads to an increase in the concentration of fast secondary electrons and, hence, to an increase in the rate of dissociation of monosilane molecules and the growth rate of silicon suboxide films. With further increase in the argon flow rate, the scattering of the electron beam becomes so large that the growth rate reaches saturation with a value of 2 nm s −1 at R = 80 and decreases .…”

Section: Resultsmentioning

confidence: 99%

Structural and optical properties of a‐SiO_x:H thin films deposited by the GJ EBP CVD method

Zamchiy

et al. 2016

In this work, hydrogenated amorphous silicon suboxide (a‐SiOx:H) thin films have been prepared by gas‐jet electron beam plasma chemical vapor deposition method (GJ EBP CVD) at a substrate temperature 260 °C. The argon to monosilane ratio R = [Ar]/[SiH4] was varied and the influence of the ratio R on the structural and optical properties was investigated. In this method, R affects an oxygen concentration in the film of the silicon suboxide. FTIR measurement showed a decrease of the oxygen concentration from 40.7 to 11% with increasing R. The analysis of FTIR spectra showed the containing a large number polysilane (Si–H2)n groups that suggest the material column structure. Optical transmission spectra were recorded to investigate the optical properties and thickness of the a‐SiOx:H thin films. The maximum of the growth rate is 2 nm s−1 at R = 80. The optical bandgap Eg was derived from Tauc plots. It was found that the increase in the oxygen concentration not only leads to the increase optical bandgap, but also to the decrease the refraction index.