Sulfur-doped diamond thin films have been synthesized using CH<sub>4</sub>/H<sub>2</sub>/Ar/H<sub>2</sub>S gas mixture by hot filament chemical
vapor deposition (HFCVD) technique. The optical properties of the films are investigated by SEM and Raman spectra.
The Gaussian line shape is used in the curve fitting for the Raman spectra. Results show that the I<sub>D</sub>/I<sub>G</sub> presents the trend
of first increase and then decrease with the increase of S/C ratio, however, an upward shift of the diamond peak is
observed. This implies residual stress in the sulfur-doped diamond thin films. Moreover, optimum experimental
conditions are proposed.
A new method is presented for measuring the electric parameters in dielectric barrier discharge (DBD), and the effect of
barrier on discharge is investigated. Results show that the number of discharge current is variable in different half period
of applied voltage, and the current pulse width is in the range of 160 to 280ns. The discharge power increases
monotonously with the applied voltage, and the maximum power is 22.62w, which corresponding power density of
5.76w/cm<sup>3</sup>. The electric field in the gas gap decreases monotonously with the increase of gas gap, and the optimum work
condition is proposed in DBD.
The Debye characteristic temperature is a useful parameter of nanodiamond thin films. In this paper, the Debye
characteristic temperature of diamond thin films is studied through X-ray diffraction intensity at a fixed temperature.
From x-ray diffraction, we can get the average crystallite size of diamond thin film. By the method of Xueshan Lu and
Jingkui Liang, the Debye-Waller factor and Debye temperature are calculated, they are B=0.010937 nm<sup>2</sup> and
Θ<sub>D</sub>=527.95K, the Debye temperature is about one-fourth of the Debye characteristic temperature of the bulk diamond
single crystal (about 2200K). The relationship between crystal size and Debye characteristic temperature is also
discussed. The Debye characteristic temperature depends on particle size. When the diamond changes from bulk
diamond to diamond films, the crystal size of diamond becomes smaller, so the Debye characteristic temperature
becomes lower. This means that the atom binding force becomes weak, and it can increase the activity of nanodiamond
The substrate temperature is one of the most important parameters for the synthesis of high quality diamond thin films in
hot filament chemical vapor deposition (HFCVD) system. Based on the principle of heat transfer, the substrate
temperature is calculated in the single hot filament system, the influence of filament height, filament diameter and
filament length on substrate temperature are also discussed. Results show that the substrate temperatures vary with the
space position. In the direction of parallel with the filament, the substrate temperatures vary smoothly, but, in the vertical
direction of the filament, the substrate temperatures change acutely. When H=8mm, L=7cm and d<sub>f</sub>=0.5mm, the substrate
temperatures are well-distributed, this will give the support of some technique parameters for the growth of large area
HFCVD diamond thin films.
Due to thermal mismatch, stresses develop in n-type diamond thin films when cooled down to room temperature from
deposition temperature. In this investigation, thermal stresses in diamond films deposited on silicon substrate are
calculated, the influence of temperature and film thickness on thermal stresses are also discussed. The results show that
thermal stresses are sensitive to deposition parameters, the thermal stresses increase with the increase of deposition
temperature, reach the maximum value of 0.724GPa at 1000k, and then begin to decrease. With the increase of diamond
thickness and substrate thickness, the thermal stresses decrease and increase respectively.
High-quality Sulfur doped n-type diamond thin films have been successfully synthesized via glow plasma assisted hot filament chemical vapor deposition using gas mixtures of methane, hydrogen, Argon and hydrogen sulfide. Impacts of the volume ratio of hydrogen sulfide to methane R<sub>S/C</sub>on the structural and physical properties of the films have been systematic ally studied using various techniques such as Hall effect measurement, x-ray diffraction (XRD) and atom force microscope. We found that the carrier mobility is 474 <i>cm</i><sup>2</sup>V<sup>-1</sup>S<sup>-1</sup> and the electrical conductivity is 1.45Ω<sup>-1</sup>·<i>cm</i><sup>-1</sup>at R<sub>S/C</sub>=6800ppm. The sheet resistivities of the films increase with increase of R<sub>S/C</sub>, reach the maximum at RS/C of 6200ppm, and then begin to decrease. Also, with increase of R<sub>S/C</sub>, a linear increase in the conductivities of the films is found, which is believed that higher R<sub>S/C</sub>is favorable for the increase of electrical conductivity of sulfur doped diamond thin films.