A. Szekeres

Structural and Optical Properties of CVD Thin Tungsten Oxide Films

Thin amorphous and polycrystalline tungsten oxide films were prepared by chemical vapour deposition at atmospheric pressure from a metalorganic precursor - tungsten hexacarbonyl. The dependence of the structural and optical properties of tungsten oxide films on the technological conditions has been investigated by XRD, Raman spectroscopy and spectroscopic ellipsometry.

Spectroscopic characterization of CVD-molybdenum oxide films

Abstract By chemical vapor deposition at atmospheric pressure using Mo(CO) 6 precursor and Ar/O 2 gas mixture, thin MoO 3 films were prepared on Si substrates. The deposition and sublimator temperatures were in the range of 150–200 and 70–90°C, respectively. Investigations of the as-deposited MoO 3 films were performed by spectroscopic ellipsometry (300–800 nm) and infrared spectrophotometry (200–1200 cm −1 ). The refractive index of the films was found to be in the range of 1.7–2.3 and the optical band gap energy, E og , estimated from the absorption analysis, was in the range of 2.76–3.14 eV. The infrared spectra exhibit the characteristic peaks for β-modification of polycrystalline material.

Enhanced gas sensing of Au nanocluster-doped or -coated zinc oxide thin films

We demonstrated that doping or covering with Au nanoclusters boosts gas sensing effectiveness of optical metal oxide sensors. The sensing response of pulsed laser deposited ZnO films as sensing element was tested by m-line technique for low concentration (1000ppm) of butane in environmental N2. The optical interrogation was performed for three types of coatings: undoped ZnO, undoped ZnO structures partially covered with Au nanoclusters, or obtained from Au (0.5wt%) doped ZnO targets. Nanocluster coating tripled the sensitivity, while doping resulted in an increase of up to 45% as compared with simple structures.

R.F. plasma annealing of as-grown defects in the Si/SiO2 system

Abstract The annealing effect of an r.f. hydrogen plasma on the interface properties in Si/SiO2 systems was investigated. The fixed oxide charge is found to be sensitive to the low temperature plasma annealing. Annealing is more effective at higher temperatures and when applied to metallized structures. With bare oxides the generation of slow states is observed whose concentration depends on the substrate temperature. A final 450 °C hydrogen anneal gives very low fixed charge densities. Comments on the annealing mechanism are also given.

Study of As2Se3 and As2Se2Te glass structure by neutron- and X-ray diffraction methods

Neutron and high-energy X-ray diffraction measurements have been performed on As40Se60 and As40Se50Te10 glasses. Both the traditional Fourier transformation technique and the reverse Monte Carlo (RMC) simulation of the experimental data have been applied to model the 3-dimensional atomic configurations. From the analysis of the partial atomic correlation functions and structure factors the first and second neighbour distances, coordination numbers and bond-angle distributions were calculated. It is established that substitution of Se by Te does not change the basic glassy network structure. For the As-Se bonding is revealed that the first neighbour distance is at 2.42 A, the average coordination numbers are CNAsSe=2.6±0.1 and CNSeAs=1.8±0.1 atoms and the three-atom-bond angle for , configurations is 95°, the same value within limit of error, as obtained from RMC calculations.

LPCVD-silicon oxynitride films: interface properties

The interface properties of silicon oxynitride films prepared by low-pressure chemical vapor deposition at a temperature of 860 ° C have been investigated analyzing the capacitance-voltage and ac conductance-voltage characteristics of the metal-SiO x N y -silicon capacitors. Consistent results for the interface trap density have been obtained from single frequency ac conductance technique, approximation C-V method and from the interface density spectrum. The post-deposition annealing results in an improvement of the interface charge properties. The contribution of the interface traps to the estimation of the fixed oxide charge has been discussed which is important for the threshold voltage control in MOS devices.

Capacitance–Voltage Characterization of LPCVD‐Silicon Oxynitride Films

LPCVD-silicon oxynitride films with different compositions were deposited on n-Si(111) substrates by reacting dichlorosilane (SiH 2 Cl 2 ) with nitrous oxide (N 2 O) and ammonia (NH 3 ) at a temperature of 860 °C varying the gas flow rate ratio of N 2 O and NH 3 . The electrical properties of the SiO x N y films were studied by analysis of the 1 MHz capacitance-voltage characteristics of the metal-SiO x N y -silicon capacitors. It has been found that with increasing amount of N 2 O in the deposition ambient the concentration of the dielectric charges in the SiO x N y /Si structures goes through a minimum, while the interface trap density gradually decreases. The nature of the defects is discussed.

Spectroscopic ellipsometry characterization of strained interface region in thermally oxidized Si(111)

Abstract The optical properties of Si/SiO 2 interface formed at 850 °C oxidation of silicon were studied by using spectroscopic ellipsometry in the range of 280–632.8 nm (4.43−1.95 eV). The results indicate a 1.0 nm thick highly stressed interface with a physical composition of Si 0.6 (SiO 2 ) 0.4 . Oxidation induced stress causes changes in the optical constants of Si substrate in the strained region beneath Si/SiO 2 interface. The thickness of this optically nonhomogeneous region is estimated to be about 5 nm.

Oxidation kinetics of hydrogen-enriched Si(100) and Si(111) surfaces

Abstract Hydrogen-enriched Si(100) and Si(111) wafers were thermally oxidized and the growth kinetics were studied by measuring the thickness and the refractive index of the oxide. The oxidation was performed in dry oxygen at temperatures of 800, 845 and 855 °C Prior to oxidation the Si surfaces were hydrogen-enriched by hydrogenation in hydrogen plasma in a planar r.f. unit. The substrates were kept at the lower electrode without heating or at a temperature of 100 °C. In the investigated thickness range of 40–200 A the growth was linear with time. The rate constant was smaller and the zero time thickness higher (as obtained from the fit of the experimental points) as compared with the case of the Si surface with wet RCA preoxidation clean only. A discussion on the role of the hydrogen in oxide growth mechanisms is included.

Charged defects in wet SiO2/Si structure modified by rf oxygen plasma treatment

In the present paper the influence of oxygen rf plasma treatment on the properties of both Si and SiO 2 sides of the wet thermal SiO 2 /Si interface was investigated. The defect concentrations of the oxide charge, dopant level and the interface trap density were obtained from capacitance-voltage (C-V) characterization. The amount of hydrogen trapped in the interfacial region was estimated from changes in the doping density of the silicon substrate. Generation and passivation of electrically active defect centers were found depending on the substrate temperature and the amount of hydrogen. Modification of the oxide and interface between Si and wet SiO 2 is inferred. Plasma promoted release from the oxide bulk of hydrogen species is suggested.