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Multilayers consisting of graphene oxide (GO) and α-Fe2O3 thin layers were deposited on the ceramic substrates by the spray LbL (layer by layer) coating technique. Graphene oxide was prepared from graphite using the modified Hummers method. Obtained GO flakes reached up to 6 nanometers in thickness and 10 micrometers in lateral size. Iron oxide Fe2O3 was obtained by the wet chemical method from FeCl3 and NH4OH solution. Manufactured samples were deposited as 3 LbL (GO and Fe2O3 layers deposited sequentially) and 6 LbL structures with GO as a bottom layer. Electrical measurements show the decrease of multilayer resistance after the introduction of the oxidizing NO2 gas to the ambient air atmosphere. The concentration of NO2 was changed from 1 ppm to 20 ppm. The samples changed their resistance even at temperatures close to room temperature, however, the sensitivity increased with temperature. Fe2O3 is known as an n-type semiconductor, but the rGO/Fe2O3 hybrid structure behaved similarly to rGO, which is p-type. Both chemisorbed O2 and NO2 act as electron traps decreasing the concentration of electrons and increasing the effective multilayer conductivity. An explanation of the observed variations of multilayer structure resistance also the possibility of heterojunctions formation was taken into account.

Reduced graphene oxide and copper oxide multilayer structures were fabricated in a planar configuration by deposition on both ceramic and Si/SiO2 substrates with interdigitated Au electrodes by the spray method. SEM (scanning electron microscopy), TEM (transmission electron microscopy), XRD (X-ray diffraction), and elemental analysis investigations indicated that graphene oxide (GO) was obtained in a form of interconnected flakes consisting of 6&ndash, 7 graphene layers for GO with the total thickness of ca. 6 nm and 2&ndash, 3 layers for rGO with the total thickness of 1nm. The lateral size of one flake reached up to 10 micrometers. Copper oxide was obtained by the wet chemical method. The number of sequential layers of the sensing structure was optimized to obtain good sensitivity and acceptable response/recovery times in response to the oxidizing nitrogen dioxide atmosphere. Both semiconductor partners revealed p-type conductivity. Formation of isotype heterojunctions between both semiconductor partners was taken into account and their influence on electrical transport explained. Optimized sensor structures revealed relative sensitivities reaching several tens of percent and acceptable response and recovery times in NO2 concentration ranged from a few to 20 ppm. Possibility of manufacturing sensors working at room temperature was shown, but at the cost of prolonged response/recovery times.

This paper presents the acetone sensing characteristics of Si-doped (1 at.%) tungsten oxide thin films prepared by glancing angle dc magnetron sputtering. The performance of Si-doped WO3 sensors in the concentration range of 0.04–3.8 ppm at operating temperatures of 150 °C–425 °C has been investigated. Doping of the tungsten oxide film with Si significantly decreases the limit of detection of acetone compared with the pure WO3 sensors reported in the literature. The gas sensor’s response ( $S$ ) to acetone was defined as the resistance ratio $S = R_{\mathrm{ air}}/R_{\mathrm{ gas}}$ , where $R_{\mathrm{ air}}$ and $R_{\mathrm{ gas}}$ are the electrical resistances for the sensor in air and in gas, respectively. The maximum response measured in this experiment was $S=40.5$ . Such response was measured in the presence of 3.8 ppm of acetone at an operating temperature of 425 °C using a Si-doped (1 at.%) WO3 thin film deposited at 300 °C and annealed at 300 °C for 4 h in air. The films phase composition, microstructure, and surface topography have been assessed by X-ray diffraction, scanning electron microscope, atomic force microscope, and energy dispersive X-ray spectroscopy methods.

In this paper, the investigation results on preconcentration of acetone at various initial concentrations are presented. The structures were made of conventional materials, such as stainless steel, quartz tube as well as fabricated in MEMS technology - micropreconcentrators. All structures have the same ‘active’ area to obtain more suitable comparison. The adsorbent materials were selected from commercial available Sigma-Aldrich Carbon Adsorbent Sampler Kit, consisting of 8 various adsorbents. The highest concentration factors were obtained by utilization of micropreconcentrator filled with Carboxen-1018, which is recommended for adsorption of C2-C3 compounds. The preconcentrators were placed into microsystem, and semiconductor gas sensor array was used as a detector unit. The microsystem was previously tested and designed for exhaled breath acetone analysis. The obtained results show that micropreconcentrator can be a useful tool for an increasing sensor sensitivity.

Graphene oxide was obtained using the modified Hummers method. Some part of samples was prepared as multilayer graphene oxide - copper oxide structures. After temperature annealing the structures decreased the resistivity enabling investigations of interaction with the ambient gas. The response to nitrogen dioxide was determined and observed changes with varying measurement temperature and gas concentration explained.

An electrospinning technology have been developed to obtain zinc oxide nanofibres doped with aluminum. Properties of the obtained nanostructures can be controlled by both the composition of a precursor and subsequent annealing treatment. The gas sensors manufactured with the use of ZnO:Al nanofibres exhibit good response to NO2 at relatively low operating temperatures. For some samples it was observed that interaction with ambient NO2 gas causes the change of conductivity from n-type to p-type at higher operating temperatures. This phenomenon was not observed for the samples annealed at higher temperature.

In this paper we present a review of research results and technical accomplishments presented by researchers from technical universities, governmental institutes and research companies during the XIIth Scientific Conference Electron Technology, ELTE 2016. This review is based on materials presented at four topical conference sessions: Microelectronics and Nanoelectronics, Photonics, Materials and Technologies, and Microsystems and also on materials presented by invited speakers at two dedicated sessions. Oral sessions were accompanied by the poster sessions. In effect about 50 papers gathered in this volume reflect the topics discussed at the Conference. A short description of technological and measurement possibilities in the laboratories of Academic Centre for Materials and Nanotechnology and also in the Department of Electronics of the Faculty of Computer Science, Electronics and Telecommunications AGH UST are given.

This paper presents investigation results obtained with the measuring system enabling detection of acetone with concentrations lower than 1 ppm. In the experiment we used both conventional preconcentrators made from materials such as stainless steel and quartz tubes and a micropreconcentrator manufactured in MEMS technology. The active volume of all preconcentrators was equal to enable comparisons of their performance. As a gas detector at the output of the measurement system we used both commercial semiconductor gas sensor and a mass spectrometer for comparison purposes. The obtained results show that the measurement system with micropreconcentrator and a commercial gas sensor can be used for detection of low level acetone present in the air exhaled by diabetics.

We design and manufacture the gas micropreconcentrator in low temperature cofired ceramics (LTCC) technology. The structure is 1.2-mm thick and has lateral dimensions of 25 × 20 mm. It consists of eight layers of LTCC green tapes with spiral-shaped channel filled with absorbing powder. Two heaters covered by the ceramic foils are embedded over and below the channel. The heaters are required for heating the adsorbent to elevated temperatures during its activation and desorption processes. In this paper, we describe the fabrication processes of a micropreconcentrator structure designed for acetone detection applications together with thermal and preconcentration measurements of the device. Commercially available adsorbents: Carboxen-1018, Carboxen-1012, and Carboxen-1003 from Sigma-Aldrich are selected and tested in order to concentrate low levels of acetone. The best concentration factor obtained is 5250.

The authors designed and manufactured the gas micropreconcentrator in micromachining technology. The structure is 1.68 mm thick and has lateral dimensions 2 cm by 2 cm. It contains the 12 cm long channel etched in Si wafer. The channel is covered from the upper side with a glass bonded anodically so as to permit for an easy inspection of the channel during the process of filling it with an adsorbent. At the bottom the Pt heater was deposited, necessary for heating the adsorbent to elevated temperatures during its activation and desorption processes. In the article the authors describe the micropreconcentrator simulations and technology processes together with thermal and preconcentration tests of manufactured structure. A few commercially available adsorbents from Sigma–Aldrich were selected and tested in order to concentrate low levels of acetone. The best concentration factor obtained was 830.

The authors manufactured conductometric type gas sensors based on ZnO nanostructures. Using electrodeposition method ZnO nanorods with good crystallinity were obtained. Application of electrospinning method allowed for easy manufacture of ZnO:Al nanofibres with varying diameter. The sensors were built in both nanowire network and a single nanowire configurations. Investigation of sensors characteristics revealed good sensitivity to nitrogen dioxide at temperatures lower than these for conventional resistance type sensors.

Solution growth of ZnO sub-micro rods enhanced by electric fieldRecently the one-dimensional ZnO nanostructures have attracted much attention in gas sensor applications owing to their increased role of the surface. The authors have obtained ZnO rods of sub-micron size using the solution growth method with the growth temperature below 100°C. Investigations indicate that the rods have a well-defined hexagonal morphology and a wurtzite structure. The best uniformity and alignment of the sub-micron crystals was however obtained when electrodeposition from aqueous solution was developed. Sizes of these rods depend on the growth parameters. Moreover electrodeposition leads to a faster growth rate of ZnO sub-micron rods (2 hrs) as compared to the growth from solution (8 hrs). After electrodeposition the rods can be easily reoriented in external electric fields by using substrates with electrodes of appropriate geometry and configuration (dielectrophoretic effect). This enables the preparation of samples which can be used in gas sensor technology.

Commonly used substrates for resistance-type oxide sensors are mainly alumina plates. Other types of ceramics, e.g. based on Low Temperature Cofired Ceramics (LTCC) technology could also be used for this purpose. This technology is well established and enables a creation of 3D structures with channels and cavities that can be formed inside a LTCC micromodule. The work describes manufacturing of the microsystem containing a gas preconcentration chamber and sensor substrates with improved thermal properties, all fabricated in LTCC technology.

The optimization of temperature control in a vacuum furnace used for selenization of Cu/In metallic precursors for CIS solar cells is described. The heat transfer between all parts of the furnace was analysed using SIMULINK programming. A system of state equations describing all elements of the object (vacuum furnace) is represented in the matrix form. The performed simulations were compared with experimental variations of temperature with time indicating very good agreement. The results obtained were utilized for the temperature control. A comparison of the constant control signal used in previous experiments with the one obtained from calculations indicates that the desired temperature profile in the furnace is obtained in a much shorter time when applying the calculated control.

Semiconductor gas sensors are essentially not selective to detect a single chemical species in a gaseous mixture and also the response of the sensor in most cases is influenced by the variations of ambient humidity and temperature. One of the solutions is the analysis of the dynamic response of a single sensor with modulated temperature. For the non-linear output signal the fast Fourier transform transform was calculated. The zero-order amplitude and the phases of higher harmonics were selected. These quantities served as input data for the fuzzy model of the sensor. The hybrid fuzzy sensor model, based essentially on Takagi-Sugeno-Kang (TSK) theory, comprised a two-level optimization algorithm. The authors elaborated that algorithm, utilizing conjugate gradient and genetic algorithm methods. At the output of the fuzzy model the concentrations of ethanol with minimized influence of humidity variations were obtained.

A novel design of gas sensor using low temperature cofired ceramics (LTCC) and thin film technologies is presented. The LTCC structure is composed essentially of two ceramic layers with interlayer thick film Pt heater, interdigitated electrodes on top, contact pads and metallic connections realised by vias. The thin films of both SnO2 and In2O3, intentionally doped and activated, were deposited on top of the structure. With some modifications of the lamination process and heat treatment parameters, the authors obtained the upper ceramic layer with the roughness not exceeding 250 nm, what was suitable for thin film technology. The films deposited onto such LTCC structure revealed the sensing properties very similar to the reference films deposited onto glass. The gas-sensitive films were tested with changing concentrations of reducing and oxidising gases in air. The necessary sensor working temperature was obtained and stabilised using a custom-built digital controller. The low heat capacity of the sensor structure enabled also a sinusoidal temperature control. The satisfactory results obtained by the authors indicate that the connection of LTCC and thin film technologies can lead to the fabrication of good quality gas sensors.

The manufacturing of CuInSe 2 (CIS) thin films by selenization of Cu–In alloy precursors in a graphite container is described. The copper–indium alloy was formed by magnetron sputtering of Cu/In multilayers. By sequential deposition of Cu and In the 20 alternate layers structure with total thickness varying from 250 to 500 nm was obtained. The Cu/In ratio was altered by adjusting the layer deposition time. The phases obtained by X-ray diffraction (XRD) for metallic precursor films were identified as Cu 2 In, CuIn, Cu 11 In 9 or CuIn 2 . To produce CuInSe 2 the alloys were annealed with elemental selenium in temperature range between 400°C and 500°C by adopting the two-step temperature profile. The selenized films were characterized using XRD to identify the phases and scanning electron microscopy to observe the surface morphology. The parameters of chalcogenization process, mainly heating temperature, time and Se pressure, influence significantly the properties of obtained CIS films.

Currently, most of gas sensors on the market are produced in thin or thick film technologies with the use of ceramic substrates. It is expected that the miniature sensors needed in portable applications will be based on one-dimensional structures due to their low power consumption, fast and stable time response, small dimensions and possibility of embedding in integrated circuit together with signal conditioning electronics. The authors manufactured resistance type gas sensors based on ZnO and WO 3 nanostructures. ZnO:Al nanorods with good cristallinity were obtained with electrodeposition method, while ZnO:Al nanofibres with varying diameters were obtained by electrospinning method. The sensors were built as a nanowire network. WO 3 films with nanocrystalline surface were manufactured by deposition of a three layer WO 3 /W/WO 3 structure by RF sputtering and successive annealing of the structure in appropriate temperature range. In effect a uniform nanostructurized metal oxide layer was formed. Investigation of sensors characteristics revealed good sensitivity to nitrogen dioxide at temperatures lower than these for conventional conductometric type sensors.

The cupric oxide (CuO) thin films are promising materials in gas sensor applications. The CuO exhibits the highest sensitivity for hydrogen sulfide, but it may be also used as a sensor for carbon monoxide or nitrogen dioxide. The sensitivity and long-term stability are critical issues in gas sensor applications. The authors present the results of investigation on nano-thin film of CuO and CuO doped with Au and Pd. The films were deposited in magnetron sputtering technology on LTCC substrates. The results of gas sensor response are presented and discussed. The long-term stability test were performed.

The authors designed and manufactured the gas micropreconcentrators in two of the most popular industry technologies: low temperature cofired ceramic (LTCC) and microelectromechanical systems (MEMS). Both structures have similar lateral dimensions: 20 mm × 25 mm × 1.2 mm for micropreconcentrator in LTCC technology and 20 mm × 20 mm × 1.68 mm for micropreconcentrator in MEMS technology. Both structures contain a 120 mm long channel filled with adsorbent material. The authors used commercially available adsorbents supplied by Sigma-Aldrich. In the paper the authors describe thermal measurements, power consumption and concentration factor tests of manufactured structures for gaseous acetone.

The principal features of amorphous semiconductorS are the short range order, the long range disorder and the coordination defects. The preservation of the Short range order resultS in a similar overall electronic structure of an amorphouS material compared to the equivalent crystal. The long range structural disorder originating from the deviations of the bond lengths and bond angles is responsible for the formation of broadened tails of localized states extending into the forbidden gap. Electronic states deep within the gap arise mostly from coordination defects. In a-Si:H these kinds of defects are threefold coordinated silicon dangling bonds in the neutral state D° when singly occupied and in the states D+ or Dwhen empty or doubly occupied. Positive correlation energy in the reaction of formation D+ and Dfrom D° defects ensures that in equilibrium most of defects are in singly

The analytical expression for the reflectance of a weakly absorbing wedge shaped thin film supported on a thick transparent substrate has been obtained. The envelopes of reflectance maxima and minima derived from that expression together with known formulae for envelopes of transmission spectrum enable calculation of optical constants and thickness non-uniformity of the film. The calculations have been applied to thin films of amorphous silicon and the results obtained have been compared with those for films considered uniform.

Real thin films, deposited by vacuum methods, exhibit thickness inhomogeneities which influence the optical transmission and reflection spectra. This is the cause of drastic shrinking of the interference fringes of both transmittance and reflectance and serious errors occur if one calculates refractive and extinction indices with the assumption of film uniformity. Influence of thickness inhomogeneity on the transmission spectrum only was discussed by several authors. In this work one obtains the analytical formula for reflectance of an inhomogeneous, wedge shaped film. Using expressions for envelopes around the maxima and minima for both transmittance and reflectance of the nonuniform films, it was possible to calculate accurate values of optical constants and thickness variation. The calculation procedure was applied to the optical spectra of a-Si : H films deposited by RF sputtering and glow discharge methods and the obtained results were compared with those for films considered to be uniform.

For several years authors have been making series of technological experiments with a-Si:H films on glass substrate by d.c. magnetron sputtering. The main intention of the research is to obtain large area solar cells and a matrix of thin film transistors for liquid crystal displays [1-3]. This study is a part of series of experiments in which the problem of the effective ohmic junction and the question of the barrier height in the thin film stuctures are investigated. Various types of sandwich structures were prepared, as shown in the Table. D.c. magnetron sputtering was used to obtain the stuctures and all the films. D.c. planar magnetron system was specially made to optimize the preparation conditions of the a-Si:H films as well as hydrogen partial pressure pH2, argon partial pressure p AS , substrate temperature Τs , input power P and substrate bias Vs. The a-Si:H films were obtained in the conditions earlier reported in [1, 2]. Schottky diodes were fabricated in a sandwich structure. Molybdenum or aluminum sputtered onto glass substrate, served as the back contact. An ohmic contact characterized by effective electron injection to a-Si:H, was only obtained if additional film of 0.3 μm polycrystalline silicon was sputtered in an 99% of argon and 1% of phosphin atmosphere. Then, the a-Si:H film and top Schottky electrode were deposited on the substrate. Active area of the junction was 0.005 cm 2 . Diode rectification ratios about 10 4 are observed at room temperature, as shown in Fig. 1. This ratio is ultimately limited by the series resistance of the quasi-neutral region which affects the forward current. The undoped hydrogenated silicon is highly resistive with p 109 Ωcm. The rectification ratio about 104 was

In order to evaluate inhomogeneity of amorphous silicon thin films in the direction normal to the film surface, a calculation procedure was adopted enabling determination of the optical constants of films with a slightly rough upper surface and with an assumed variation of refractive index. Calculations were based on measured transmittance and reflectance at normal incidence in the region of interference fringes.

Measurements of photoconductivity decay from the steady state for samples of amorphous silicon and silicon-carbon alloys were carried out using the experimental set-up with a Pockels cell as a light chopper. The developed electronic switching circuit allows measurements of decay times ranging down to microseconds. The advantage of the adopted method of light switching is that one can easily control the light intensity and photon energy. From knowledge of the photoconductivity decay time and the value of the steady state photoconductivity for a given sample, the carrier drift mobility can be calculated.

Metal oxide semiconductor gas sensors with modulated working temperature should reveal small thermal time constant in comparison to the time constants of chemical reactions between gas atmosphere and sensitive layer. In such case analyzed sensor response is dominated with specific phenomena originated from these reactions. A way the sensors are mounted has big influence on the sensor thermal time constants. In experiments authors used gas sensors with ceramic and micromachined silicon substrates glued to the case or suspended on thin wires. Although mechanical stability and durability of glued sensors are better, the lower power consumption and lower time constants are possible with sensors mounted using thin wires.

Rapid Temperature Processing (RTP) methodology is widely applied in thin-film photovoltaic materials technology due to high quality of fabricated cells and also perspectives for their mass manufacturing. This paper describes a RTP device structure which contains the graphite reactor for selenization of Cu/In or Cu/In/Se precursors. Strong nonlinearity of radiative energy transfer makes RTP controlling difficult so it still needs to be improved. Using mathematical model of the device, we are proposing the method of process controlling. Experimentally obtained temperature profiles of Rapid Temperature Processes are presented and compared with temperature profile of typical CIS selenization graphite reactor. Presented steering procedure, based on our model, gives improves by decreasing time needed for selenization and simultaneously reducing costs of the process.

The objective of this work was the investigation of CdS grown by CBD on commercial glass and glass covered by transparent conductive oxide (TCO) substrates. Both TCO and CdS are window layers influencing the photovoltaic response of the cell. CBD technology offers the possibility of the deposition of a thin uniform film with a minimal thickness on a rough substrate surface. CBD growth of CdS using uncoated glass substrates enabled optimization of deposition parameters, e.g. concentrations of CdSO/sub 4/, NH/sub 3/ and thiourea SC(NH/sub 2/), bath temperature and deposition time. Successively glass plates coated with TCO (SnO/sub 2/, ZnO) layers were used as substrates. Both as-grown and air-annealed samples were studied. Investigation of optical transmission in the range 350 - 2200 nm, using Perkin - Elmer Lambda 19 spectrophotometer enabled the evaluation of heat treatment and selected technological parameters on CdS and CdS/ TCO bilayer optical properties. SEM and AFM surface morphology investigations indicate that CdS films reproduce morphology and roughness of the polycrystalline TCO sublayer. That conformal growth and thickness uniformity of cadmium sulfide thin films deposited by CBD technique are presumably the main reasons of their superior quality as buffer layers in CIS solar cells.

Amorphous hydrogenated silicon‐germanium alloys a‐Si1−xGex:H in the form of thin films were prepared by rf sputtering and chemical vapor deposition methods with x varying from 0 to 0.63. Optical transmission, reflection, and photoconductivity measurements in the visible and near‐infrared regions of light enabled determination of the optical energy gap, band‐tail states distribution, and density of defect states near midgap. Dark conductivity and photoconductivity were measured in the temperature range of 300–500 K. Electronic band structure (density of states versus energy) for a‐Si0.74Ge0.26:H thin film was derived on the basis of optical measurements, dark conductivity, and photoconductivity.

The authors investigated microwelding of Pt wires and ribbons to PdAg, PtAg and Au thick film contact pads deposited in a form of single, double or triple layer structures. The weldings were carried out using modern Hughes MCW 550 microwelder. The welding current pulse power and duration as well as welding head electrodes distance and force were varied to obtain the maximum adhesion of the lead. In order to evaluate the contacts performance mechanical strength tests and aging tests were carried out. Scanning electron microscope investigations of the connection area allowed for optimization of the contact pad thickness and lead wire diameter.

We have deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD), under particular conditions of high H2 dilution and high power density, undoped and phosphorus doped (µc‐SiC:H films. We have obtained n‐doped films with a high band‐gap (E04 up to 2.1 eV) and a high dark conductivity (σ4 up to 10 S cm‐1) which are promising materials for window layers in solar cells. Thermo Electric Power (TEP) measurements allowed to identify the type of majority carriers. The dark conductivity and the Hall mobility have been obtained as a function of temperature in the range 80‐480 K.

Temperature-modulated metal-oxide gas sensors exhibit different behavior from sensors operating in an isothermal mode. Such temperature-modulated sensor response is affected by stimulating excitation, sensor structure, sensitive layer preparation etc. Due to different reaction rates dependent on modulating temperature, the response yields a special signature for the investigated gas atmosphere. The response can be analyzed using different pattern recognition and artificial intelligence methods. As a result, one can achieve an improvement of selectivity and drift reduction. It is also possible to accomplish a qualitative and quantitative analysis of gas mixtures using a single sensor. One of the most important issues is the selection of proper parameters of a signal that modulates the heater temperature. The range of temperature variations should be chosen according to the gas type and its concentration to achieve good sensitivity. The period of the excitation signal also influences the sensor response and has to be chosen above the value of gas/semiconductor reaction time constant. In this paper the authors describe the ways in which a temperature-modulating signal is selected and discuss the possibility of using a dynamic sensor response to quantitatively determine the concentrations of two gases in a mixture with the help of one sensor.

The mechanism of the reactive sputtering of SnSb and InSn alloys in a reactive atmosphere was investigated. The oxygen content in the reactive mixture and the composition of the target influence the sputtering of the target and the properties of the films.

Transparent and conductive Cd2SnO4 and CdIn2O4 thin films have been prepared by reactive sputtering from Cd-Sn and Cd-In alloy targets in an Ar+O2 atmosphere. Electrical conductivities of the order of 105 Ω−1 m−1 with the optical transmission as high as 90% were easily attained. Hall and thermoelectric power measurements indicate that charged point defects are responsible for the scattering of conduction electrons. The optical constants of the films were computed from the transmission and reflection measurements in the visible and near-IR spectral ranges using a special procedure based on a model of an inhomogeneous film with a rough surface.

Cd2SnO4 n-conducting thin films have been prepared by DC reactive sputtering from Cd-Sn alloy targets. The concentration of conduction electrons was varied over the range 7*1025-3*1026 m-3 by the post-deposition heat treatment as well as by the variation of the content of the target. Temperature dependence of carrier concentration and Hall mobility in the temperature range 77-380K show the films to be degenerate semiconductors. Oxygen vacancies and interstitial cadmium ions are the postulated charge defects. The existence of neutral defects was also taken into account.

Transparent and conductive CdIn2O4 thin films are prepared by dc and rf reactive sputtering from a CdIn alloy target. The temperature dependence of the carrier concentration and that of the Hall mobility as well as the spectral dependence of the imaginary part of dielectric permittivity indicate that CdIn2O4 is a n-type semiconductor in which charged point defects are responsible for the scattering of conduction electrons. Two types of scattering centres, i.e. ionized donors and oxygen traps are considered to account for the observed dependence of the Hall mobility on carrier concentration.

Cadmium stannate (Cd2SnO4) films were prepared by d.c. reactive sputtering from Cd-Sn alloy targets. The electrical and optical properties of these films were found to depend both on the oxygen concentration in the ArO2 atmosphere during deposition and on the composition of the target. The best figure of merit of about 9.8 × 10−3ω−1 was obtained at atomic ratios of 2:1 and 3:1 for Cd:Sn and Ar:O2 respectively.

The chemical composition and the phase composition of thin non- stoichiometric films of SnOx were investigated. The films were fabricated by the sputtering of a metallic tin target in a reactive Ar-O2 atmosphere. The contents of the SnO2, αSnO and βSn phases in the film were determined using X-ray diffraction and Mossbauer spectroscopy. Nuclear backscattering spectroscopy was used for the chemical analysis. It was concluded that, at low oxygen concentrations in the reactive mixture (less than 6%), the SnO2 phase is dissolved in the SnO matrix. The crystalline phase of SnO2 appears at higher oxygen concentrations. The electrical conductivity is affected by the non-stoichiometry of the films and vacancies in an oxygen sublattice act as donor centres.

A simple model of the conduction mechanism, with the assumption of a non-parabolic conduction band, has been applied to wide band gap, degenerate thin oxide films. The scattering mechanism is explained in terms of intergrain potential barriers and charged point defects. A comparison between theoretical results and experimental data is made for SnO 2 and CdIn 2 O 4 .