Electrical properties of bulk silicon dioxide and SiO2/Si interface formed by tetraethylorthosilicate (TEOS)-oxygen plasma enhanced chemical vapor deposition

The electrical properties of bulk silicon dioxide and the SiO₂/Si interface formed by TEOS/O₂ PECVD were investigated. Additionally, the gas phase in the glow discharge was investigated using OES analysis under various experimental conditions. Changes of TEOS/O₂ ratio and the deposition temperature influenced the electrical properties of silicon oxide films. With decreasing TEOS/O₂, ratio, the electrical properties of bulk silicon dioxide and the SiO₂/Si interface were improved. This is thought to be due to the decrease of carbon impurity in the growing oxide film. At higher deposition temperatures, the oxide films had good electrical properties, which is thought to be due to the change of structure in the oxide film. From C–V analysis for all experimental conditions, the P_b center defects were observed near E_v+0.25eV and E_v+0.73eV in the Si band gap. The magnitude was influenced by process parameters such as the TEOS/O₂ ratio and the deposition temperature. From OES analysis, the main emission peaks observed in the glow discharge were from CO, CO ₂ ⁺ , CH, and C. With decreasing TEOS/O₂ ratio, the emission intensity of CH decreased and that of CO increased.     

The electrical model of polycrystalline CdSe Thin films

Studies of the electrical properties of polycrystalline CdSe thin films evaporated onto ruby substrates show that the mobility of charge carriers depends on the longitudinal electric field in some ranges of the field intensity. A structural model of a polycrystalline thin film has been developed by other authors. A diode model for the boundary regions has also been used.By analogy with other work we decided to construct an electrical model of the CdSe films that were studied. The proposed model contains two kinds of elements—diodes and resistors. This model was analysed numerically to verify its static electrical characteristics. The qualitative resemblance of the I-U, U_b-U and U_m-U characteristics of the model and the real sample (where U_b is the total voltage drop on all grain boundary regions and U_m the total voltage drop on all microcrystallites) is shown. It seems that after development the proposed electrical model can be used with advantage in the analysis of the electrical properties of semiconductor polycrystalline thin films.     

Synthesis of c-axis oriented AlN thin films on different substrates: A review

Highly c-axis oriented AlN thin films have been deposited by reactive sputtering on different substrates. The crystallographic properties of layered film structures consisting of a piezoelectric layer, aluminum nitride (AlN), synthesized on a variety of substrates, have been examined. Aluminum nitride thin films have been deposited by reactive pulsed-DC magnetron sputtering using an aluminum target in an Ar/N₂ gas mixture. The influence of the most critical deposition parameters on the AlN thin film crystallography has been investigated by means of X-ray diffraction (XRD) analysis of the rocking curve Full-Width at Half Maximum (FWHM) of the AlN-(0 0 0 2) peak. The relationship between the substrate, the synthesis parameters and the crystallographic orientation of the AlN thin films is discussed. A guide is provided showing how to optimize these conditions to obtain highly c-axis oriented AlN thin films on substrates of different nature.     

Deposition of Conductive Films on Semiconductor Substrates via Molybdenum Hexacarbonyl Decomposition in Glow Discharge

The properties of films deposited via molybdenum hexacarbonyl decomposition in glow discharge are found to depend strongly on the nature of the substrate and the sign of bias. Molybdenum films are obtained on SiO₂/Si at any bias and on Si, GaAs, InP, and InAs substrates at positive bias. At negative bias, molybdenum silicide films are produced on Si. The films deposited at positive bias have the highest electrical conductivity. X-ray diffraction, Auger electron spectroscopy, and sheet resistance data are used to elucidate the mechanism of film deposition via molybdenum hexacarbonyl decomposition in glow discharge.     

Electrical and optical properties of µc-SiH films

Microcrystalline silicon films have been found quite useful in amorphous silicon solar cells as a contact material in n-i-p cells. Microcrystalline silicon films are obtained when amorphous silicon films are prepared by R.F. glow discharge of SiH₄ + H₂ at higher power ratings. These films possess higher conductivity as well as high transmission than amorphous silicon films. The present paper reports the preparation technique ofμc-SiH films using R.F. capacitive glow discharge of hydrogen-diluted silane. X-ray studies andtem studies of the films indicate microcrystallinity of the films. The electrical and optical properties are also reported.     

Effect of AlN layer thickness on structure and magnetic properties of FePt/AlN multilayers

FePt (50 nm) and [FePt(xnm)/AlN(1, 2, 3 nm)]₁₀ (x=2, 3 nm) films were prepared by RF magnetron sputtering technique, then were annealed at 550 °C for 30 min. This work investigates the effect of AlN layer thickness on structure and magnetic properties of FePt/AlN multilayers. Superlattice (0 0 1) peaks can be found in the grazing incidence X-ray diffraction of FePt and [FePt (3 nm)/AlN (1, 2, 3 nm)]₁₀ films, which indicate that the FCC phase has been partially transformed into ordered L1₀ phase. Compared with the single layer FePt film, superlattice (0 0 1) peaks of FePt/AlN multilayers are weak and wide, which indicates that the introducing of AlN hinders the growth of FePt particle, and also shows the introducing of AlN is not beneficial to the transformation from FCC phase to L1₀ phase. In addition, the low-angle XRD spectra show the layered structure of FePt/AlN has been broken after annealing. The coercivities, particle size, intergrain exchange interactions of FePt/AlN films are decreased with increasing AlN layer thickness.     

Preparation and application in p-n homojunction diode of p-type transparent conducting Ga-doped SnO2 thin films

The direct preparation of p-type transparent conducting Ga-doped SnO₂ thin films and their fundamental application in transparent p-n homojunction diode were realized. The films were grown in an active oxygen ambient using reactive rf magnetron sputtering without post-deposition annealing involved. This method improved the electrical properties of the films while maintaining their optical transparency. By growing a p-type thin film on commercial n-type SnO₂:F-coated glass, transparent p-n homojunction diode was obtained. It exhibits a distinct current-voltage rectifying characteristic, manifesting this p-type thin film and the fabrication technology are suitable for industrial applications.     

The electrical properties of polycrystalline ZnIn2Te4 thin films

Thin films of ZnIn₂Te₄ are grown onto glass substrates by the flash evaporation technique. Electrical properties such as electrical resistivity and activation energy were studied with different substrate temperatures ranging from 300 to 623 K. It is observed that the film grown at a substrate temperature of 523 K is a single phase polycrystalline stoichiometric film with minimum electrical resistivity. The effect of the film thickness on the electrical properties of ZnIn₂Te₄ thin films grown at a substrate temperature of 523 K has been studied. The experimental data can be satisfactorily explained on the basis of the Fuchs-Sondheimer theory.     

On the properties of AlN thin films grown by low temperature reactive r.f. sputtering

In this paper we report on the growth of c-axis-oriented AlN thin films by low temperature reactive r.f. sputtering and the results of their examination and analysis in a variety of ways. In addition to using other substrates, we fabricated c-axis- oriented AlN films on aluminium film substrates. A hexagonal column structure was observed in the morphology of replicas of the natural surfaces of films. As well as the dielectric constant ε, the resistivity ϱ, the breakdown field E_p and the refractive index n, curves of ε versus frequency f, ε versus temperature T and conductivity σ versus T were measured. The IR absorption spectrum of an AlN film sputtered at low temperature coincides with that of an AlN film sputtered onto a high temperature substrate and of a bulk crystal, which remains unchanged after annealing. The band gap E_g = 5.9–6.0 eV, which remains unchanged after annealing in N₂ at 900°C. Theoretical calculation of the dispersion curve of surface acoustic waves by an AlN/glass structure shows that the curve is very level in the range hk = 0.2–0.6. The capacitance-voltage curve of an Al/AlN/Si structure is given in this paper.     

A study on the interface and bulk charge density of AlN films with sputtering pressure

An attempt to correlate deposition-induced effects and the morphological properties with the electrical properties of the aluminum nitride (AlN) films have been made. The AlN film was sputter deposited on silicon while increasing the pressure in steps from 2×10⁻³ to 8×10⁻³ mbar. An X-ray diffractogram revealed that the intensity of (0 0 2) orientation increased till 6×10⁻³ mbar pressure, but it changed to (1 0 0) orientation of the AlN film at 8×10⁻³ mbar. The FTIR spectra of the absorption band of the films were observed around 682 cm⁻¹ and became prominent at 6×10⁻³ mbar. A decrease in the grain size was seen by SEM images at 8×10⁻³ mbar. The AFM measurements revealed that the surface roughness varied from 1.56 to 3.24 nm with pressure. It was found that the insulator charge density (Q_in) increased from 1.4×10¹¹ cm⁻² to 1.3×10¹² cm⁻² with increase in pressure. On the other hand, the interface state density (D_it) was found minimum (7.3×10¹¹ eV⁻¹ cm⁻²) at 6×10⁻³ mbar. It is found that presence of the Q_in and D_it are primarily governed by the sputtering pressure of the AlN film.     

Effect of the interface on the electrical properties of an indium zinc oxide/SiOx multilayer

In this work, indium zinc oxide (IZO) films have been deposited on a polyethylene terephthalate substrate coated with an SiO_x film. Based on a comparative investigation of an IZO monolayer and an IZO/SiO_x multilayer, it is shown that oxygen has a great effect on the electrical properties of the thin films. A mechanism is described to explain the influence of the introduced SiO_x buffer layer. It is considered that an interfacial layer has come into being at the interface between the SiO_x layer and IZO layer, and the properties of this layer have been evaluated. Moreover, the electrical properties of the IZO/SiO_x multilayer have been successfully improved by controlling the oxygen content of the interfacial layer.     

Properties and coating rates of diamond-like carbon films produced by R.F. glow discharge of hydrocarbon gases

We studied the properties of films produced by cracking various hydrocarbon gases in an r.f. glow discharge. Mass spectrometry studies and optical spectroscopy of the glow discharge were performed during the experiments.We found that the production rates for the films increased with the molecular weight for gases having the same structural form, e.g.C₄H₁₀ had a higher coating rate than CH₄ under the same plasma conditions. Also the sputter-etch rate of the films depended on both the substrate material and the hydrocarbon gas used.Films several microns thick were manufactured onto steel substrates and showed a microhardness of more than 3000 kgf mm^-2.     

Positive flat band voltages measured on MIS diodes consisting of evaporated CdS films

SiO₂ films with very low losses have been produced by the decomposition of Si(C₂H₅O)₄ in an r.f. glow discharge. Loss-tangents of less than 10^-4 and break-down voltages of about 1 × 10⁷ V are obtainable by this method. The optical and electrical properties of these films are discussed.     

Deposition and characterization of reactive magnetron sputtered aluminum nitride thin films for film bulk acoustic wave resonator

This work studies the relationship between the deposition process parameters and the properties of sputtered c-axis-oriented aluminum nitride (AlN) thin films. AlN films were deposited on a Pt electrode by reactive magnetron sputtering under various deposition conditions. The films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). A polycrystalline AlN film with highly c-axis-preferred orientation was achieved. The XRD rocking curve was 2.7°. The FESEM photographs also show that the AlN film has a dense hexagonal surface texture with uniform grain size and a highly ordered column structure.     

Plasma-enhanced chemical vapour deposition of AlN coatings on graphite substrates

Graphite substrates have been covered with aluminium nitride (AlN) layers prepared by plasma-enhanced chemical vapour deposition from AlBr₃-N₂-H₂-Ar gas mixtures. The glow discharge (frequency, 13.56 MHz; power, 50–500 W) was generated by an r.f. induction coil. The graphite substrate mounted on a grounded graphite susceptor was inductively heated up to a temperature in the range 200–800 °C. The mass of the deposit per square centimetre was determined as a function of reaction time, total gas pressure, substrate temperature, r.f. power, gas flow velocity and AlBr₃ concentration. The morphology of the AlN layers was examined by scanning electron microscopy. Fine-grained polycrystalline AlN films were grown at 700 °C under a total pressure below 10 Torr. Translucent polycrystalline AlN films having a 〈001〉 preferred orientation were deposited at a total pressure in the range 10–40 Torr.     

Fourier transform infrared spectroscopy characterization of AlN thin films grown on sacrificial silicon oxide layers via metal organic vapor phase epitaxy

Aluminum nitride (AlN) films were grown using metal organic vapor phase epitaxy techniques on Si (111) substrates patterned with silicon oxide (SiO_x) stripes and the vibrational properties of these films were investigated by Fourier transform infrared (FTIR) techniques. The grown films contained a predominantly wurtzite AlN phase. The AlN film on SiO_x was prone to corrosion when subjected to wet etching in buffered hydrofluoric acid solution thereby changing the material properties of the AlN film on SiO_x. The change in the material properties of the AlN films on SiO_x can be gauged from the decrease in the relative integrated areas under the A1 (TO) and E1 (TO) modes of the AlN film. The analysis shows that FTIR is a viable tool for investigating the material properties of AlN thin film structures with lateral dimensions as low as 100 μm.     

Growth of pseudocubic perovskite-type SrRuO3 thin films on quartz substrate using pulsed laser deposition method

Strontium ruthenium oxide (SrRuO₃) thin films have been grown using pulsed laser deposition technique on silicon, Pt coated silicon and quartz substrates. The effect of substrate temperatures on the structural, microstructure, and electrical properties of the SrRuO₃ films on quartz substrate has been investigated using XRD, SEM, AFM and four-probe method, respectively. The lowest resistivity at room temperature for the SrRuO₃ thin film on quartz substrate has been achieved at substrate temperature of 700 °C. Furthermore, the comparisons of SrRuO₃ thin films deposited on various substrates have been done with respect to structural, microstructural and electrical properties. XRD patterns exhibit that all thin films are a single phase, pseudo-cubic perovskite structure. Study of surface morphology shows that grain size and roughness varies with respect to substrate. It is observed that SrRuO₃ thin films yield larger grain size and root mean square roughness on Pt/Si substrate. Investigation of electrical properties shows that SrRuO₃ thin films can serve the purpose of the bottom electrode in dielectric and ferroelectric devices.     

Electrical properties of glow discharge amorphous SiNx: H thin films

Amorphous SiN_x:H films were prepared by the r.f. glow discharge of SiH₄N₂H₂ mixtures and their electrical properties were investigated as a function of x. Efficient doping is possible in these films and a high photosensitivity as well as a low conductivity of 10^?14 S cm^?1 are obtained by adding B₂H₆ in the molar ratio 10^?4 to SiH₄N₂ in the gas phase. These interesting properties are achieved by the reduction in the hopping conduction due to the incorporation of nitrogen.     

Deposition and characterization of thin SiOx films

Thin (less than 500 Å) homogeneous SiO_x (1.5 < x < 2.0) films prepared from the glow discharge reaction of silane or a silane derivative with an oxidant such as nitrous oxide or oxygen have shown considerable promise as dielectric layers. The chemical composition and properties of these films are relatively insensitive to the glow discharge geometry, the gas composition and the power. Oxidant-rich plasma mixtures provide denser films and thus greater protection against atmospheric attack on the underlying material. The films were characterized using infrared spectroscopy, Auger depth profile analysis, transmission electron microscopy, scanning electron microscopy, multiple-drop liquid contact angle measurements and ellipsometry.     

Characterization and Low Temperature Study of Iron Telluride Thin Films Upon Ageing and Oxygen Ion Irradiation

The occurrence of superconductivity in iron telluride thin films has been observed upon ageing. The superconducting transition is found to be very robust under an application of magnetic fields up to 10 T. Infrared and Raman spectroscopic characterization of the aged films reveal the formation of Fe_1+δTeO _x upon ageing. As an alternative method of introducing oxygen in FeTe thin film, oxygen ion irradiation has also been carried out It is found that the irradiated film becomes increasingly disordered and ultimately transforms to an amorphous phase upon increasing the irradiation dose. Investigation of electrical resistivity and optical reflectivity of the irradiated FeTe films indicates an interesting possibility of an ion irradiationinduced phase change memory material in analogy to the phase change characteristics of laserirradiated FeTe films.