Characterization Of CVD Research Articles

Elastic characterization of CVD diamond by static and dynamic measurements

The present paper describes two different nondestructive approaches for the direct identification of the elastic constants of thin square isotropic plates. First a static method is presented, by which the identification of the Young's modulus and Poisson's ratio is carried out by the full field measurement of the out-of-plane displacements detected on the upper surface of the plate in two biaxial bending tests. Then a dynamic method is illustrated, by which the elastic constants are determined from two different natural frequency of a free vibrating plate. Both techniques, previously verified on a carbon steel specimen, have been applied to a CVD diamond specimen; a comparison between the two approach is reported and the influence of the measurement errors is also discussed.

Thermoluminescence characterization of CVD diamond film exposed to UV and beta radiation

Thermoluminescence (TL) properties of diamond films grown by microwave and hot filament CVD techniques were studied. The main purpose of the present work was to characterize the thermoluminescence response of diamond films to ultraviolet and beta radiation. The thermoluminescence excitation spectrum exhibits maximum TL efficiency around 210-215 nm. All samples presented a glow curve composed of at least one TL peak and showed regions of linear as well as supralinear behavior as a function or irradiation dose. The linear dose dependence was found for up to sixteen minutes of monochromatic UV irradiation and 300 Gy for beta irradiated samples. The activation energy and the frequency factor were determined and found in the range of 0.33-1.7 eV and 5.44 x 10 2 - 5.67 x 10 16 s -1 , respectively. The observed TL performance is reasonable appropriate to justify further investigation of diamond films as radiation dosimeters keeping in mind that diamond is an ideal TL dosemeter since it is tissue-equivalent and biological compatible.

Processing and Characterization of CVD c-BN Films and c-BN/Diamond Bilayers

ABSTRACTThe paper reports the syntheses of c-BN films by the reaction of B2H6 and NH3 in the hydrogen and argon mixture using microwave plasma-assisted chemical vapor deposition (MPCVD). The effects of NH3/B2H6 ratios, hydrogen addition, pulsed-DC substrate-bias voltage and diamond as bufferlayer on the formation of c-BN were investigated. As-grown films are characterized by FTIR, grazing-incidence XRD, and SEM. The NH3/ B2H6 = 3 was selected to obtain a better crystallized BN films with moderate deposition rate. When the hydrogen content was at 85 vol.% in the gas mixture and the substrate bias at −200 V, the maximum c-BN content about 65 % was obtained. However, the film was easily cracked in a few hours. The film deposited at lower substrate biasing of −100 V could preserve for a few days without peeling off, although it had lower c-BN content about 40 %. Nanocrystalline diamond film, deposited from 1 vol.% CH4/Ar plasma, as bufferlayer can promote the heteroepitaxial growth of c-BN, resulting in 80 % c-BN content. The c-BN/diamond bilayer were adherent with a total thickness of 1.2 μm.

Deposition and characterization of CVD – MoO3 thin films

This paper presents results on molybdenum oxide films deposited by APCVD process from Mo(CO) 6 in a low-temperature range - 125-200°C. We first study the correlation between CVD-process growth parameters and the structure of MoO 3 films, from one side, and the relation between their structure and optical properties, from the other side. We present a study basically on the influence on the structure of the temperature - the deposition and the post-deposition annealing ones and the influence of the vapor pressure of Mo(CO) 6 . The structure of the films is studied by different methods including infrared spectroscopy. The purpose is to see what kind of additional information can supply the IR measurements on the structure of the films in dependence of the CVD-process parameters.

Non-destructive characterization of CVD diamond films on cemented carbide cutting tools

Abstract Cemented carbide tools coated with diamond have been proved to show superior performance for machining non-ferrous alloys, especially aluminum alloys. The development of efficient CVD technologies for the deposition of polycrystalline diamond up to an industrial scale allows their broader industrial application. However, the strong influence of the deposition conditions and of the substrate morphology on the film properties requires adequate characterization methods to optimize the diamond coatings and to control the deposition process. To overcome the lack of suitable characterization methods, investigations were performed to combine structural properties (Raman spectra), Young's modulus of the coatings, and mechanical erosion tests (sandblast test), and the machining behavior of diamond-coated cemented carbides (drilling of AlSi10Mg). Whilst Raman spectroscopy characterizes the quality of the diamond structure, Young's modulus allows the presence of defects and the quality of the interface to be evaluated. Depending on the deposition technology and the pretreatment of the substrates, an enhanced porosity and weaker interface strength were detected. A correlation of Young's modulus with the results of the sandblast test was found.

Growth and characterisation of CVD diamond wires for X-ray detection

Abstract In order to gain insight into the mechanism of diamond growth on metallic wires (50–500 μm diameter), we have investigated the deposition process in a hot filament chemical vapour deposition (HFCVD) reactor. A two-dimensional model of our HFCVD reactor was developed in order to interpret the experimental data which indicate an evident influence of the substrate wire diameter on the gas species concentration and on the diamond growth rate. The theoretical model indicates a reduction of the growth rate as the substrate diameter increases due to the reduction of hydrogen and the active radicals concentrations at the substrate as its growth area increases. In view of a possible application of such samples as X-ray detectors, we investigated their electrical properties by analysing the current/voltage characteristic in a metal/diamond/metal geometry at different temperatures. The activation energy of the conductivity is found to be dependent on the applied electric field. The experimental data support a Poole-Frenkel conduction with overlapping centres. Finally the response of our diamond wires to X-ray radiation flux was investigated. A sensitivity of about 5 × 10 −6 A s Gy −1 was measured under a 100 keV Bremsstrahlung X-ray flux and the photocurrent is almost linear with respect to X-ray tube current.