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Showing papers in "Journal of Materials Science: Materials in Electronics in 1993"


Journal ArticleDOI
TL;DR: The structural, electrical and optical properties of epitaxial semiconductor layers, delta-doped with impurity atoms, are reviewed in this article, where the electrostatic attraction between free carriers and ionized dopants results in a V-shaped potential well, perpendicular to the dopant plane, which confines the carriers into a quasi-two-dimensional sheet, and quantizes their energy into a series of subbands.
Abstract: The structural, electrical and optical properties of epitaxial semiconductor layers, delta-doped with impurity atoms, are reviewed. The majority of the discussion relates to GaAs, the most-studied material, but where possible, results for Si and other semiconductors will be presented. Although the ideal situation is one of dopant atoms confined to a single atomic plane, there are several factors, such as diffusion and segregation, which broaden the profiles, and techniques to minimize these effects are discussed. The electrostatic attraction between free carriers and ionized dopants results in a V-shaped potential well, perpendicular to the dopant plane, which confines the carriers into a quasi-two-dimensional sheet, and quantizes their energy into a series of sub-bands. This has significant consequences for the electrical and optical properties of the layers, and results of such measurements on these structures are presented. Several features of delta-doped layers are attractive for exploitation in devices, and this is illustrated by reference to a number of novel or improved device designs.

48 citations


Journal ArticleDOI
TL;DR: In this paper, the window layer of CdS/CulnSe2 solar cells have been prepared by vacuum evaporation at various deposition conditions, and the effect of the deposition conditions on the properties of DSS films was investigated by measuring electrical resistivity, optical transmittance and reflectance.
Abstract: 1 Μm CdS films for the window layer of CdS/CulnSe2 solar cells have been prepared by vacuum evaporation at various deposition conditions. Deposition rates were 0.73 and 3.3 nms−1, and substrate temperature ranged from 50 to 225 ‡C. The effect of the deposition conditions on the properties of CdS films was investigated by measuring electrical resistivity, optical transmittance and reflectance.

26 citations


Journal ArticleDOI
TL;DR: In this paper, a carbon (carbon black and/or graphite)/polyesterimide resin system has been used as a material for polymer thick-film resistors and the physical and chemical properties of this system as a function of curing temperature were evaluated by means of resistance measurements during the curing process, thermogravimetric analysis, adhesion measurements and scanning electron microscopy examinations.
Abstract: A carbon (carbon black and/or graphite)/polyesterimide resin system has been used as a material for polymer thick-film resistors. The physical and chemical properties of this system as a function of curing temperature were evaluated by means of resistance measurements during the curing process, thermogravimetric analysis, adhesion measurements and scanning electron microscopy examinations. The temperature range between 250 and 300 ‡C has been chosen as the most suitable. The basic electrical properties and the resistance stability to low and high temperature shocks and humidity exposure have been evaluated in relation to the conductive filler used in the ink.

18 citations


Journal ArticleDOI
TL;DR: In this paper, the preparation of γ-Fe2O3 from the thermal decomposition of ferrous oxalate dihydrate and hydrazine hydrate precursors was studied employing differential thermal analysis (DTA), X-ray diffraction (XRD), infrared and magnetic susceptibility measurements.
Abstract: The preparation of γ-Fe2O3 from the thermal decomposition of ferrous oxalate dihydrate and ferrous oxalato hydrazinate precursors was studied employing differential thermal analysis (DTA), X-ray diffraction (XRD), infrared and magnetic susceptibility measurements. Ferrous oxalate dihydrate was precipitated from solution following the standard precipitation technique. The synthesis of ferrous oxalato hydrazinate was carried out by two methods. The wet chemical method reported in the literature was adopted to precipitate the compound from ferrous chloride solution. In the second method ferrous oxalate dihydrate was equilibrated with hydrazine hydrate vapour in a desiccator. The resultant product was found to be anhydrous ferrous oxalato hydrazinate. The decomposition end-products of these complexes were X-ray characterized and magnetic measurements were done. Ferrous oxalate dihydrate yielded mainly γ-Fe2O3 upon controlling the atmosphere during decomposition. However, autocatalytic decomposition of hydrazinated complexes formed a mixture of γ-Fe2O3 and α-Fe2O3. Efforts were made to increase the γ-Fe2O3 content by controlling the atmosphere during decomposition of these complexes.

16 citations


Journal ArticleDOI
TL;DR: In this article, the effect of calcining temperature on gas sensitivity and resistance in wet air was observed with elements of SnO2 thick film and the results were interpreted as a function of the crystallite size.
Abstract: The effect of calcining temperature on gas sensitivity and resistance in wet air was observed with elements of SnO2 thick film. The results were interpreted as a function of the crystallite size. As the crystallite size reduced, the sensitivity to H2 gas enhanced at temperatures lower than 300‡C, but at those higher than 350‡C it did not. The temperatures showing the minimum resistance in air and the maximum sensitivity to H2 gas decreased with reduction of the crystallite size. The temperature variations were assigned to the change of the activation energies of the oxygen adsorbates. It is suggested that the decrease of activation energies is one of the reasons for the sensitivity enhancement with the fine powder.

14 citations


Journal ArticleDOI
TL;DR: The optical nonlinear property of an Au colloid-doped glass was measured by degenerate four-wave mixing (DFWM) experiments using a frequency-doubled Nd:YAG laser with 7 ns pulse duration as discussed by the authors.
Abstract: The optical non-linear property of an Au colloid-doped glass was measured by degenerate four-wave mixing (DFWM) experiments using a frequency-doubled Nd:YAG laser with 7 ns pulse duration. The pulse duration of the phase-conjugate reflection was 4 ns, indicating the fast response time of the glass. The third-order susceptibility χ(3) was estimated to be 2.5 × 10−11 e.s.u. (3.5 × 10−19 m2 V−2). The photodarkening effect was not observed and the phase-conjugate reflection was stable against the laser irradiation.

12 citations


Journal ArticleDOI
TL;DR: In this article, the diffusion mechanisms for the dopants are briefly reviewed, and for silicon-doped material a more detailed discussion is provided because of its technological importance, and there has been no critical review of the recent progress in silicon diffusion mechanisms.
Abstract: Impurity-induced disordering seems to be a general phenomenon affecting all III–V materials. This paper reviews this phenomenon. Before the available data on impurity-induced disordering is discussed, the diffusion mechanisms for the dopants are briefly reviewed, and for silicon-doped material a more detailed discussion is provided because of its technological importance. Moreover, there has been no critical review of the recent progress in silicon diffusion mechanisms. In zinc-diffused multi-quantum wells and superlattices the mechanism for the enhancement of the interdiffusion seems to be primarily by the fast diffusion of group III interstitials whose concentration has been significantly increased over their equilibrium value by the diffusion of the dopant. For silicon impurity-induced disorder the situation is less clear. However, it is certain that the effect of the position of the Fermi level on the native defect concentrations plays a significant role in the disordering mechanism. The study of the other dopants which cause diffusion-induced disordering is less advanced. For n-type dopants there is an argument which suggests that they all have a common cause, namely the increase in the group III triply charged vacancy which is caused by the increase in the Fermi energy. This will be explored in this review. A brief discussion of ion implantation-induced disordering is also provided. This essentially provides a bibliography of the past work in this field. It is clear, for at least one dopant, that there needs to be some damage to the crystal before the enhancement of the interdiffusion occurs. However, for other dopants too much damage reduces the enhancement of the intermixing.

12 citations


Journal ArticleDOI
TL;DR: In this article, the influence of the process parameters such as flow ratio of the reactant gases, pressure, substrate temperature, r.f. power, time of deposition and electrode spacing on the deposition and etch rates were investigated and experimental results were presented.
Abstract: Silicon nitride films were deposited by a plasma-enhanced chemical vapour deposition technique using silane-ammonia as the reactant gas mixture. The influence of the process parameters such as flow ratio of the reactant gases, pressure, substrate temperature, r.f. power, time of deposition and electrode spacing, on the deposition and etch rates were investigated and experimental results are presented.

11 citations


Journal ArticleDOI
TL;DR: In this article, thin films of AgSbTe2 with different thicknesses were prepared by thermal evaporation on glass substrates held at room temperature and the films were all found to be semiconducting in nature.
Abstract: Thin films of AgSbTe2 with different thicknesses were prepared by thermal evaporation on glass substrates held at room temperature. The films were all found to be semiconducting in nature. The film resistivity was found to be a function of inverse thickness and was discussed on the basis of the effective mean free path model. The activation energy was found to be a linear function of the inverse square of film thickness. It was attributed to the quantization of the momentum component of charge carriers normal to the film plane.

9 citations


Journal ArticleDOI
TL;DR: In this article, the properties of island manganese (Mn) films with mass thicknesses 2, 4, 6, 8 nm on Corning 7059 glass substrates at ambient temperature were investigated.
Abstract: Island manganese (Mn) films of mass thicknesses 2, 4, 6, 8 nm were deposited on Corning 7059 glass substrates at ambient temperature. The deposition took place in vacuum by the thermal evaporation technique. The dependence of the d.c. resistance of the as-deposited Mn films on time (ageing) was studied in air at a room temperature of 20 ‡C over a period of 110 H. It was found that the increase in resistance lasts for relatively short intervals, in comparison with many other island films, before the resistance attains a stable value. The length of the time intervals decreases with increase of film thickness. The response of the stabilized Mn films to longitudinal and transverse induced strains was investigated and the corresponding gauge factors were deduced. The gauge factor increases with decrease of film thickness. The sensitivities of the present films to the two types of strain are comparable. The data of the research are discussed with the view that the quantum mechanical tunnelling model is the mechanism responsible for the electrical conduction in our films.

8 citations


Journal ArticleDOI
TL;DR: In this paper, a field-assisted ion exchange was carried out between soda-lime-silica glass tubes and molten PbCl2 at 823 K for 2 h under constant potential of 12 V. The influence of the exchange on the bulk d.c and a.c. electrical conductivity was investigated.
Abstract: Field-assisted ion-exchange was carried out between soda-lime-silica glass tubes and molten PbCl2 at 823 ‡K for 2 h under constant potential of 12 V. The field-assisted ion-exchange leads to the formation of a lead-exchanged layer underneath the glass surface. The influence of the exchange on the bulk d.c. and a.c. electrical conductivity was investigated and compared with that of the glass before ion-exchange. The d.c. conductivity of the exchanged glass showed an activation energy higher than that of the glass before ion-exchange. The higher activation energy was attributed to the lower mobility of lead cations in the exchanged layer in comparison with that of sodium cations. The a.c conductivity of the exchanged glass showed an increase in the dielectric constant and a decrease in the dielectric loss. These findings suggest that lead cations enter the glass network in modifying positions in the exchanged glass. The results also support the data previously obtained that one lead cation from the molten PbCl2 replaced two sodium cations from the glass.

Journal ArticleDOI
TL;DR: In this article, the thermodynamic properties of AsH3 and its subhydrides AsH and AsH2 have been evaluated from critically assessed or estimated spectroscopic data.
Abstract: The thermodynamic properties of AsH3 and its subhydrides AsH and AsH2 have been evaluated from critically assessed or estimated spectroscopic data. The calculation of thermodynamic functions (free-energy function, entropy, enthalpy, and heat capacity) is based on statistical thermodynamics. For the first time, for all three species a complete set of these functions has been generated between 0 and 1600 K in tabular form. A combination of the free-energy functions with the standard enthalpies of formation of hydrides (derived from the photoionization mass-spectrometric bond energy values of Berkowitz) permits the determination of the gas phase composition in the pyrolysis of AsH3 during the MOMBE (CBE), HS-MBE, or MOCVD growth of III–V epitaxial layers that include As. Using a free-energy minimization technique, the equilibrium concentrations of AsH, AsH2, AsH3, As, As2, As4, H and H2 have been obtained at 1.013, 3.039 × 103 and 1.013 × 105 Pa (1 atm) in the temperature range between 800 and 1500 K. In the case of MOMBE, under equilibrium conditions in the hydrate cracker, the removal of carbon-containing radicals or oxygen is facilitated by atomic H and AsH with partial pressures of ~3.33 × 10−4 and 1.87 × 10−5 Pa, respectively, at 1300 K. In contrast, in low pressure MOCVD the species AsH and AsH2 are equally prominent, while in atmospheric pressure MOCVD the dominant subhydride is AsH2.

Journal ArticleDOI
TL;DR: In this paper, the width of the compositional undulation induced by spinodal decomposition in sintered bodies increased with increasing starting particle sizes, which resulted from micro-compositional heterogeneity in the form of a solid solution within a TiO2/SnO2 secondary sphere.
Abstract: Spherical TiO2/SnO2 powders were prepared from the TiCl4-SnCl4 aqueous solution by ultrasonic spray pyrolysis. The particle size, particle-size distribution and morphology of the powders were studied in relation to concentration of source solutions and reaction temperatures. The width of the compositional undulation induced by spinodal decomposition in the sintered bodies increased with increasing starting particle sizes, which resulted from micro-compositional heterogeneity in the form of a solid solution within a TiO2/SnO2 secondary sphere.

Journal ArticleDOI
TL;DR: In this article, the ternary phase diagrams for Ga-As-W, Re-Ga, and Si were investigated with powder samples annealed in silica capsules and analyzed by X-ray diffraction.
Abstract: The ternary phase diagrams for Ga-As-W, Ga-As-Re and Ga-As-Si have been investigated with powder samples annealed in silica capsules and analysed by X-ray diffraction. All three isothermal sections at 800 ‡C are dominated by a two-phase GaAs-M equilibrium (M = W, Re, Si). Additional literature data on the Ga-As-Si system are critically evaluated and the invariant reactions and the liquidus surface are developed. The binary Re-Ga edge system was studied with additional DTA and SEM-EDX experiments and a new compound ReGa5 was detected which forms in a peritectic reaction at 764 ‡C.

Journal ArticleDOI
TL;DR: In this article, a lead titanate-based ceramics with different microstructures were prepared from PbO-TiO2 gels with equimolar and non-equimolar mixtures of the oxides.
Abstract: Lead titanate-based ceramics with different microstructures were prepared from PbO-TiO2 gels with equimolar and non-equimolar mixtures of the oxides. Deviations from the initial compositions were found in the sintered materials. As a consequence, microstructures with different grain sizes and secondary phases were developed in the resultant ceramics. These microstructures had a strong influence on the piezoelectric behaviour of the materials obtained.

Journal ArticleDOI
TL;DR: In this article, a microporous polymeric membrane suitable for use as the separator for lithium/Cu (II) rechargeable batteries and lithium/thionyl chloride primary batteries is discussed.
Abstract: Lithium batteries have been recognized as advanced high-performance and high-power sources because they provide light weight, high energy density and high voltage. The quality of these type of batteries is determined by the efficiency of electron transfer in an electrolyte as well as the microporous structure of the membrane separator. In this report, we describe the development of a superior ETFE (polyethylene tetrafluoroethylene) microporous polymeric membrane suitable for use as the separator for lithium/Cu (II) rechargeable batteries and lithium/thionyl chloride primary batteries. The requirements for a microporous membrane to be employed in these lithium batteries are discussed. We report the membrane fabrication and membrane performance in both primary and secondary batteries.

Journal ArticleDOI
TL;DR: Extended structural defects in both α-Hgl2 crystals grown in solution or from the vapour-phase were studied by optical microscopy, light scattering, SEM operated in cathodoluminescence and in secondary electron mode, X-ray topography, neutron, γ- and Xray rocking curves and oscillating crystal X-Ray diffraction.
Abstract: Extended structural defects in both α-Hgl2 crystals grown in solution or from the vapour-phase were studied by optical microscopy, light scattering, SEM operated in cathodoluminescence and in secondary electron mode, X-ray topography, neutron, γ- and X-ray rocking curves and oscillating crystal X-ray diffraction. The observed dislocations were compared with theoretically calculated dislocations. Dislocation loops, having diameters ranging from 2 Μm to 500 Μm, are observed on all low index faces. Hohlstellen (lens-shaped voids) having axes along the [0 0 1] direction, less than 1 Μm in thickness, and diameters lying in the (001) planes, ranging from 2 Μm to 10 Μm are characteristic defects. Observed plastic deformations like glide sheets and bands, tilt and twist boundaries, kink and fatigue bands, ridges and rumplings were characterized. Growth rings, spherical void inclusions 10–30 Μm in diameter, orthogonal walls of forest screw dislocations parallel to 1 00 planes, and streaks (planar void sheets crossing the (001) planes) were only observed in crystals grown from the vapour-phase. Cross-penetration twins having (1 1 4) twin planes are described. The possible formation of stacking faults was analysed. The mosaicity of solution-grown crystals ranges from 1′ to 6′. A characteristic cellular structure, having a cell size ranging from 2 um to 10 Μm, was observed in all the crystals examined and correlated to local deviations from the stoichiometric composition. Solid lens-shaped inclusions, having diameters ranging from 3 Μm to 500 Μm and thicknesses ranging from 0.3 Μm to 50 Μm, respectively, are entrapped in many crystals and correlated to spiral hillocks observed on 001 growing faces.

Journal ArticleDOI
TL;DR: In this article, the gamma irradiation of non-linear resistances shows a pronounced effect on their characteristics, such as voltage-and light-dependent resistances, although they lose their main features at high doses (140 Mrad).
Abstract: Gamma irradiation of non-linear resistances shows a pronounced effect on their characteristics. Force-dependent resistances made of polymer materials exhibit high sensitivity to low gamma-doses down to kilorads. In the case of voltage- and light-dependent resistances, the samples have proved to be resistant to gamma-rays, although they lose their main features at high doses (140 Mrad). On the other hand, for temperature-dependent resistances, no permanent damage is determined after exposure to 200 Mrad, while their resistance decreases as a function of the temperature rise due to gamma exposure. Proposals of using such a property in calorimetry, in the field of gamma dosimetry, are given, tested and proved to be satisfactory.

Journal ArticleDOI
TL;DR: In this paper, the effect of platinum addition on the superconducting properties of YBa2Cu3O7−x (123) compound was studied from the metallurgical point of view.
Abstract: We have studied the effect of platinum addition on the superconducting properties of YBa2Cu3O7−x (123) compound and elucidated from the metallurgical point of view the mechanism of formation of the fine dispersion of Y2BaCuO5 (211) particles in YBa2Cu3O7−x superconductor prepared by a melting method. In this study, the amounts of BaCuO2 and CuO-rich phases unreacted during the peritectic reaction were markedly decreased by the 211 powder addition. The 211 particles of Pt-free sintered samples were 8–10 Μm in size, but in 1 wt% Pt-added samples 211 particles were finely dispersed in the 123 matrix and the size of 211 particle was about 1–2 Μm. The critical temperature (Tc,zero) of Pt-doped samples was 91.5 K and the transport critical current density (Jc) of Pt-doped samples was much more than 104A cm−2. The high Jc and fine dispersion of 211 particles of Pt-doped YBa2Cu3O7−x superconductor are attributed to Ba4CuPt2O9 compounds formed during the partial melting, which were considered as nucleation sites of 211 particles, rather than Pt itself.

Journal ArticleDOI
TL;DR: In this paper, electrical conductivity measurements were carried out for some Schiff bases derived from 2-hydroxy-1-naphthaldehyde with o-, m- and p-phenylenediamines and their metal complexes with some tri- and tetravalent ions.
Abstract: Electrical conductivity measurements were carried out for some Schiff bases derived from 2-hydroxy-1-naphthaldehyde with o-, m- and p-phenylenediamines and their metal complexes with some tri- and tetravalent ions. It has been concluded that the complexes have slight semiconducting properties. The conductivity and the activation energy were found to depend on the molecular structure of the complex as well as the ionic potential of the metal ion. The current-voltage dependence was studied for some complexes which indicated an ohmic conduction.

Journal ArticleDOI
TL;DR: In this paper, high-resolution electron microscopy was used to determine grain sizes, atomic arrays and crystallographic details present in the films as a function of the growing parameters used.
Abstract: Tin oxide films were deposited by spray pyrolysis on KBr and glass substrates. Conventional and high-resolution electron microscopy were used to determine grain sizes, atomic arrays and crystallographic details present in the films as a function of the growing parameters used. Optical and electrical properties were also measured and related to the structural details observed. The existence of SnO and Sn3O4 phases was revealed in films obtained at low substrate temperatures.

Journal ArticleDOI
TL;DR: In this article, the phase transition is probably a consequence of thermal rotation into resolved cis and trans configurations; the frans form conducts electricity with a lower activation energy assisted by the molecular resonance.
Abstract: Diazoaminobenzene shows semiconducting properties and a phenomenon of phase transition. The semiconducting properties arise as a result of high molecular resonance induced by intramolecular hydrogen bonding at the cliazo linkage. The phase transition is probably a consequence of thermal rotation into resolved cis and trans configurations; the frans form conducts electricity with a lower activation energy assisted by the molecular resonance. Thermal rotation into the more thermally stable cis form reduces the molecular resonance so that the resultant form conducts electricity with a higher activation energy. Unexpectedly, chelation with the favoured d-block element, Cu, reduces the electrical conductivity which is evidenced by a reduced electric dipole moment. Chelation appears to proceed favourably at the cis form, since the resultant complex conducts electricity with a similar high activation energy, a result of prohibited proton exchange. Restricted rotation in the Cu chelate explains conduction via a single phase. Consistent data from 1H-NMR, i.r. and u.v.—visible spectra do confirm the proposed structural interpretation.

Journal ArticleDOI
TL;DR: In this paper, the electrical behavior, thermal expansion coefficient, and mechanical properties of fabricated substrate materials are evaluated, and as-sintered substrates possess the following characteristics: low dielectric constant of 4-5 at 1 MHz, a loss factor smaller than 0.2% at 1MHz, and a thermal expansion of 3.57 × 10−6
Abstract: In current microelectronics packaging applications, low-temperature fired substrates with low dielectric constant are required. Formulations of SiO2, B2O3, Al2O3, and CaO have been used as substrate materials which can be sintered as low as 1000‡C in air. The electrical behaviour, thermal expansion coefficient, and mechanical property of the fabricated substrate materials are evaluated. The as-sintered substrates possess the following characteristics: low dielectric constant of 4–5 at 1 MHz; a loss factor smaller than 0.2% at 1 MHz; and a thermal expansion of 3.57 × 10−6‡C−1 which is very close to that of silicon (3.5 × 10−6‡C−1).

Journal ArticleDOI
TL;DR: In this article, multiple-arc analysis is used in conjunction with a generalized relaxation time distribution (GRTD) to derive an equivalent electric circuit model for dielectric materials that exhibit frequency dispersion.
Abstract: Multiple-arc analysis is used in conjunction with a generalized relaxation time distribution (GRTD) to derive an equivalent electric circuit model for dielectric materials that exhibit frequency dispersion. The validity of this new methodology is examined by comparing reported measurements of a.c. conductance and capacitance of a polymeric dielectric with those obtained from the equivalent circuit prediction. The values are shown to agree satisfactorily over the frequency range 100 to 850 kHz.

Journal ArticleDOI
TL;DR: The charge transfer complexes produced by the reaction between picric acid and some aniline derivatives were prepared using infrared and nuclear magnetic resonance spectroscopy aiming to throw more light on their molecular structure as discussed by the authors.
Abstract: The charge transfer complexes produced by the reaction between picric acid and some aniline derivatives were prepared. The prepared charge transfer complexes (CTC) were investigated using infrared and nuclear magnetic resonance spectroscopy aiming to throw more light on their molecular structure. It was proved that a proton transfer interaction takes place between PiOH and x'Ph.NH2 leading to the formation of PiO- and x-Ph.NH~ ions. The normal x-x* electronic interaction takes place by transferring an electron from the aniline ring to the picric acid. The semiconducting properties of the CTC were investigated. All the prepared complexes were proved to have a semiconducting character within the temperature range investigated.

Journal ArticleDOI
TL;DR: In this article, a micro-Raman system was used to analyze the structural properties of crystalline silicon, showing that changes in the physical properties of the material, introducing grain boundaries, dislocations and cracking, result in a strong modification of the Raman spectrum.
Abstract: Laser-assisted processes are currently used in silicon technology. The response of the material to the laser beam depends strongly on its own physical properties and on the laser power density. The use of a microRaman system, allows the structural characteristics of the material to be analysed by varying the excitation laser power density on the sample over a large power range with a submicrometre lateral resolution. Results are reported on microindented crystalline silicon, showing that changes in the physical properties of the material, introducing grain boundaries, dislocations and cracking, result in a strong modification of the Raman spectrum. These spectral changes are enhanced for increasing laser power densities. Several mechanisms are pointed out as possible sources of the observed spectral modifications. These results show that Raman microprobe is a very promising technique for the diagnosis of technologically processed semiconductors and devices.

Journal ArticleDOI
Vesselin Shanov1, C. Popov1, Borislav Ivanov1, A. Souleva1, G. Peev1 
TL;DR: In this paper, a new experimental approach for growth rate determination of microdimensional aluminium stripes written by laser-induced chemical vapour deposition (LCVD) was developed, where the aluminium lines were obtained by pyrolysis of trimethylal aluminium (TMA) on (100) silicon monocrystalline wafer using the focused beam of a copper bromide vapour laser.
Abstract: A new experimental approach for growth rate determination of microdimensional aluminium stripes written by laser-induced chemical vapour deposition (LCVD) was developed. The aluminium lines were obtained by pyrolysis of trimethylaluminium (TMA) on (100) silicon monocrystalline wafer using the focused beam of a copper bromide vapour laser. Quantitative determination of the deposit was performed by its chemical removal from the substrate into a solution and further analysis performed using inductively coupled plasma atomic emission spectroscopy. Using this analytical method, dependences of the aluminium quantity on the partial pressure of TMA and the laser power were obtained. The growth rate at direct writing with a pulsed visible laser was calculated on the basis of aluminium quantity determinations. It is demonstrated that the proposed experimental approach could be successfully used for kinetic studies of LCVD processes.

Journal ArticleDOI
TL;DR: In this article, nonlinear resistors having current-limiting capabilities at lower field strengths and voltage-limitting characteristics (varistors) at higher field strengths, were prepared from sintered polycrystalline ceramics of (Ba0.6Sr0.4),Ti0.97Zr0,03)O3+0.3 at % La, and reannealed after painting with low-melting mixtures of Bi2O3 + PbO + B2O 3.
Abstract: Non-linear resistors having current-limiting capabilities at lower field strengths, and voltage-limiting characteristics (varistors) at higher field strengths, were prepared from sintered polycrystalline ceramics of (Ba0.6Sr0.4)(Ti0.97Zr0.03)O3+0.3 at % La, and reannealed after painting with low-melting mixtures of Bi2O3 + PbO +B2O3. These types of non-linear characteristics were found to depend upon the non-uniform diffusion of lead and the consequent distribution of Curie points (Tc) in these perovskites, resulting in diffuse phase transitions. Tunnelling of electrons across the asymmetric barrier at tetragonak-cubic interfaces changes to tunnelling across the symmetric barrier as the cubic phase is fully stabilized through Joule heating at high field strengths. Therefore the current-limiting characteristics switch over to voltage-limiting behaviour because tunnelling to acceptor-type mid-bandgap states gives way to band-to-band tunnelling.

Journal ArticleDOI
TL;DR: In this paper, the energy gap of approximately 100 nm thick films of the Se1−xSb x system was investigated using an optical transmission method, and it was found that the gap decreases linearly with increasing Sb concentration.
Abstract: The energy gap (Eg) of approximately 100 nm thick films of the Se1−xSb x system has been investigated using an optical transmission method. Eg is found to decrease linearly with increasing Sb concentration in Se1−xSb x films. No anomalous behaviour in Eg is observed at x = 0.4 as reported earlier by Wood et al.

Journal ArticleDOI
TL;DR: In this article, the a.c. conductivity for polyvinyl alcohol (PVA)-CoCl2 composites prepared by a casting method has been measured at different frequencies (0.1-10 kHz) in the temperature range 300-450 K.
Abstract: The a.c. conductivity for polyvinyl alcohol (PVA)-CoCl2 composites prepared by a casting method has been measured at different frequencies (0.1–10 kHz) in the temperature range 300–450 K. At constant temperature, the frequency dependence of a.c. conductivity, Σ(Ω), was found to fit the established equation Σ(Ω) = AΩs quite well. On the other hand, the temperature dependence of a.c. conductivity suggested an electronic hopping conduction mechanism in a thermally assisted electric field. Various theoretical mechanisms have been discussed to clarify the conduction processes in these samples. The correlated barrier hopping (CBH) mechanism, proposed by Elliott, was found to be the most appropriate one.