S. Charvet

Nanocrystalline silicon thin films prepared by radiofrequency magnetron sputtering

Abstract The effects of the hydrogen dilution and pressure on the structural and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) films deposited at 250°C by radiofrequency (RF) magnetron sputtering method have been studied in a large range of total pressure (1–15 Pa) and H 2 dilution percentage (30–100%) in the gas phase mixture (Ar+ x % H 2 ). A combination of Raman spectroscopy, infrared (IR) absorption, X-ray diffraction, DC electrical conductivity and intrinsic stress measurements has been used to characterize the films. Only SiH 2 and (SiH 2 ) n bonds essentially in grain boundaries, corresponding to well-defined doublets in the bending (844–877 cm −1 ) and the stretching (2083–2100 cm −1 ) vibrational modes regions, have been detected. The best properties in terms of structure (crystalline volume fraction) and electrical conductivity of the nc-Si films are obtained for H 2 percentage of 70%, where the crystalline volume fraction f c is approximately 80% for 5 Pa and increases up to 92% with increasing pressure up to 15 Pa. An increase of approximately three orders of magnitude in the room temperature DC electrical conductivity is also obtained for these deposition conditions. The intrinsic stress is very low and not significantly affected by the changes in the crystalline volume fraction.

Correlation between plasma parameters, microstructure and optical properties of sputtering magnetron CNx films

Abstract Analysis of carbon nitride films (CN x ) deposited by radio frequency (RF) magnetron sputtering on crystalline silicon, under different target self-bias, is reported. Plasma characterisation was performed using mass spectroscopy (MS) and the properties of films were determined in their as deposited state using elastic recoil detection analysis (ERDA), nuclear reaction analysis (NRA), X-ray photoelectron spectroscopy (XPS), infrared absorption, transmission spectroscopy and photothermal deflection spectroscopy (PDS) experiments. A good correlation is observed between the variation of N/C ratio and the growth rate. The resulting changes in the microstructure can be analyzed in terms of surface processes, nitrogen incorporation within the films and the Csp 2 content.

Stoichiometry and infrared absorption of amorphous a-C1-xNx : H carbon nitride films

Stoichiometry, bonding configurations and structural properties of plasma-deposited hydrogen-rich amorphous carbon nitride a-C1−xNx:H (0<x<0.20) films have been investigated using infrared and Raman vibrational spectroscopies, along with x-ray photoemission spectroscopy at the C and N K-edges. With increasing N incorporation in a-C1−xNx:H, the total H content decreases slightly and C–H vibrations are progressively replaced by N–H vibrations. The dominant bonding configuration is C=N throughout the composition range, although C=N and C–N saturate above 10 N at. %, and C≡N configurations steadily increase throughout the stoichiometry range. A strong conjugation of imine (C=N) and nitrile (C≡N) groups with aromatic rings is evidenced while the Raman signature of the sp2 C phase indicates an increase in the D to G peak intensity ratio, related to some ordering of the sp2 clustered phase.

Optical behavior of reactive sputtered carbon nitride films during annealing

The effect of annealing temperature (TA) on amorphous carbon nitride (a-CNx) thin films, deposited using radio-frequency (rf) magnetron sputtering technique of a graphite target in a pure nitrogen (N2) atmosphere at different rf power, is investigated. Film composition was analyzed using Fourier transform infrared absorption (FTIR), Raman spectroscopy, optical transmission, and photothermal deflection spectroscopy (PDS) experiments. The refractive index and the mass density were determined using optical transmission spectroscopy and elastic recoil detection analysis measurements. The microstructure analysis revealed the porous character of films, which decreases slowly with increasing annealing temperature (TA). The results of Raman spectroscopy, FTIR, and PDS experiments demonstrate that the films below 400°C mainly consist of aromatic cluster component and polymeric component. With increasing TA, the progressive graphitization of the material is accompanied by a high disorder form of Csp2 sites.

On the induced microstructure changes of the amorphous carbon nitride films during annealing

The analysis of the stress release and structural changes caused by postdeposition thermal annealing of amorphous carbon nitride thin films (a‐CNx) has been carried out. The a‐CNx films were deposited on Si (100) using reactive radio frequency (rf) magnetron sputtering of a high-purity graphite target in a pure nitrogen plasma under various different rf powers. Combined Fourier transform infrared (FTIR), Raman spectroscopy, transmission spectroscopy, photothermal deflexion spectroscopy, and residual stress measurements were used to fully characterize the films. Annealing of the samples in vacuum at temperature up to 600°C produces changes in their structural properties and the intrinsic stress. These changes are found to be strongly dependent on both the deposition conditions and microstructure changes occurring within the films during heating. FTIR spectra showed the existence of N–C sp3, NC sp2, and CN triple bonds in the deposited films. The analysis of the spectra versus annealing temperature (TA) r...

An optical wireless bistable micro-actuator

An optical wireless bistable micro-actuator is presented in this paper. The bistable mechanism is based on antagonistic pre-shaped double beams, which have the merits of simple pre-load operation and symmetrical output force. The bistable micro-actuator was fabricated with deep reactive ion etching (DRIE) technique using silicon on insulator (SOI) wafer. The bistable beam has a thickness of 25 μm and a depth of 400 μm. The stroke of the bistable micro-actuator is 300 μm. An 8 μm thick compressive SiO2 layer is deposited on one side of the strip shaped (0.1×1×3 mm) shape memory alloy (SMA) active element, acting as the biasing spring. The SiO2 layer created a two way memory effect and eliminated the load effect of SMA element. Stroke of SMA element is tested. The wireless actuation was realized by laser heated SMA active element.

Optical remote control of an electromagnetic digital actuator

In this paper, an optical remote control of a digital actuator array is introduced. Driven by a field-programmable gate array (FPGA) based systems, the control permits an electromagnetic actuator to move in response to the reception of serial displacement orders through a wireless optical link. This optical communication is based on a laser diode for emitting the different orders and a selective photodiode for the reception of them. The paper presents a serial data transmission link using one particular wavelength in order to control an actuator along its two displacement axes. This work is structured into two parts: The evaluation of the optical link performances, and the demonstration of the effective remote control of an elementary digital actuator.