Some d.c. properties of evaporated thin aluminium fluoride films

The measurements of some d.c. properties of samples of evaporated aluminium fluoride thin films sandwiched between metal electrodes are reported. The technique of Rutherford scattering of megaelectronvolt alpha particles was used to study the stoichiometry and impurity content of the films. Measurements were made in the temperature range 77–393 K, and the thickness of the films ranged from 800 to 4000 Å. At high temperatures and high fields the conduction process can be explained on the basis of the Poole-Frenkel mechanism in amorphous materials, as described by Hill. At low temperatures the conductivity fits the Mott relation $\text{σ ∝ exp(-T}{}_0\text{/T)}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$. The breakdown electric field, measured as a function of film thickness d in the range 700–7500 Å, obeys the Forlani-Minnaja relation.     

The aging effect of the thermoelectric power of thin copper films

The thermoelectricpower, referenced to bulk copper, of thin films of copper about 150 Å thick was measured by preparing a thin film bridge between two copper wires which served as leads. This arrangement produces two junctions between the thin film copper and the bulk copper. The two junctions were maintained at a temperature difference which was measured using a calibrated copper-constantan thermocouple. It was found that the thin film-to-bulk thermoelectric power varies with time and can be fitted to an equation of the form

$\text{S = S}{}_{\mathrm{<mtext>F</mtext>}}\text{(1?}\text{e}{}^{\mathrm{-\lambda t}}\text{)}$

where λ depends on temperature. The constant λ in the equation has values very close to those found from thin film resistance aging measurements, suggesting that the same mechanism is responsible for both aging phenomena. The heated junctions is negative, in agreement with a simple electron diffusion model of thermoelectric power.     

Dispersion-strengthened copper-based materials formed by high rate magnetron/plasmatron sputtering

A magnetron/plasmatron source was used for sputtering CuTi(0.7 wt.%)Fe(0.9 wt.%) to produce fine-grained (diameter approximately 1 μm) dispersion-strengthened films of thickness 30–100 μm with finely dispersed particles (size less than 25 Å). After sputtering without heat treatment the CuTiFe films showed a large increase in strength (σ_0.2 ≈ 700 MPa; σ_B ≈ 750 MPa; microhardness HV_M ≈ 3000 MPa) and an electrical conductivity of $\text{25–30}\text{m}\text{Ω}{}^{-1}\text{mm}{}^{-2}$, i.e. about half the conductivity of pure copper. The strengthened films remained stable to post-deposition annealing at up to 650 °C.     

Related structural,electrical and photoelectrical properties of vacuum-deposited GaP thin films

GaP thin films with thicknesses from 0.1 to 0.6 μm were prepared by the thermal evaporation of the compound GaP onto quartz substrates at temperatures from ambient temperature to 740 °C. The properties of the films depended strongly on substrate temperature and deposition rate. With increasing substrate temperature the film structure changed from amorphous to textured polycrystalline with a strong [100] texture. The temperature of the amorphous-to-crystalline transition depended on deposition rate and was found to be 360 and 400 °C for deposition rates of 2 and 10 Å s^-1 respectively. At these temperatures the electrical resistivity of the films fell sharply from 10⁸ Ω cm to a minimum value of $\text{5 × 10}{}^4\text{Ω}\text{cm}$, after which it increased again with increasing temperature. The amorphous films exhibited a moderate photosensitivity with a maximum value near the temperature of the structural transition; above this temperature the films lost their photosensitivity completely. The spectral dependence of the photoconductivity was measured and an attempt was made to interpret the observed spectra.     

Formation and properties of metallic organotin films

Semiconductive and conductive films of metallic appearance are formed by glow discharge of appropriate organometallic compounds. Tetramethyltin is used as a starting compound for the film-forming experiments. The resulting films contain carbon, tin and hydrogen with a carbon-to-tin atomic ratio of 2.5 or less. These films are semiconductors with conductivities between 2 × 10^-1 and $\text{1 × 10}{}^{-2}\text{Ω}{}^{-1}\text{cm}{}^{-1}$. Transmission electron microscopy shows the films to be amorphous. Films of a certain composition are transformed to β-Sn on exposure to an electron beam. Thermal treatment increases the conductivity gradually to values of about $\text{1 × 10}{}^2\text{Ω}{}^{-1}\text{cm}{}^{-1}$.     

Zur silicidbildung in dünnen Molybdän- und Wolframschichten

Continuing our previous work, we have investigated silicide formation during the production of molybdenum or tungsten thin films (electron beam evaporation) on single-crystal silicon and during subsequent heat treatments in the temperature range T = 723–823 K.Using X-ray thin film thickness measurements, a parabolic WSi₂ film growth clearly dependent upon evaporation time was observed during film production as well as during tempering. As the thickness of the MoSi₂ thin films in this work is smaller by nearly one half, their measured values show a larger scatter. It was not possible to determine exactly the growth kinetics of the MoSi₂ thin films from measurements by X-rays, but a $\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ dependence was deduced.     

Thermal expansion of corundum structure Rh2O3

The directional thermal expansion coefficients of the corundum structure form of Rh₂O₃ were determined from room temperature to 850°C by x-ray diffraction methods. Rh₂O₃ has a lower thermal expansion and is less anisotropic in thermal expansion than alumina. The directional thermal expansion coefficients of Rh₂O₃ expressed in second degree polynominal form are: $\text{“α}{}_{\mathrm{<mtext>a</mtext>}}\text{” = 5.350 ×10}{}^{\mathrm{?6}}\text{+ 1.281 ×10}{}^{\mathrm{?9}}\text{T}\text{? 1.133 ×10}{}^{\mathrm{?14}}\text{T}{}^2\text{/°}\text{C}$ and $\text{“α}{}_{\mathrm{<mtext>c</mtext>}}\text{” = 5.246 ×10}{}^{\mathrm{?6}}\text{+ 6.369 ×10}{}^{\mathrm{?9}}\text{T}\text{? 7.480 ×10}{}^{\mathrm{?14}}\text{T}{}^2\text{/°}\text{C}$.     

Ionic conductivity of Li4GeO4, Li2GeO3 and Li2Ge7O15

The ionic conductivity of polycrystalline samples of three lithium germanates: Li₄GeO₄, Li₂GeO₃, and Li₂Ge₇O₁₅, has been determined using a c techniques and complex plane analysis. Conductivities at 400°C are 8.7 × 10^?5, 1.5 × 10^?5, and $\text{1.4 × 10}{}^{\mathrm{?7}}\text{(Ω·}\text{cm}\text{)}{}^{\mathrm{?1}}$ respectively. The conductivity of Li₄GeO₄ rises appreciably in the range 700–750°C.     

Interdiffusion in the CuAu thin film system at 25°C to 250°C

Interdiffusion in the Cu-Au system has been studied in the temperature range 25–250°C using conductivity measurements and Auger in-depth composition profiles. Samples were prepared by three different methods: (1) Au was evaporated over evaporated Cu, (2) Au was electroplated over electroplated Cu and (3) Au was electroplated over wrought (bulk) Cu.The conductivity data for both the evaporated and the plated samples could be represented by $\text{ΔG}\text{G}\text{= 0.030{1?exp(?10}{}^5\text{t}\text{k}\text{)} ? (}\text{t}\text{k}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ where G is the conductance, t the time and k is an acceleration factor which is a function of temperature and thickness. Interdiffusion coefficients D? were obtained from the conductivity data by using the measured acceleration factors. These data can also be used to predict sheet conductance changes for reasonable thicknesses of Cu and Au films. Auger composition profiles were obtained by analysis beginning at the original Au-to-air interface and proceeding through the Au film into the Cu. Three distinct regions were found: (1) Cu oxide growth at the original Au surface, (2) a plateau region of a few atomic per cent Cu in the Au film and (3) a zone around the original Au-Cu interface where the Cu concentration rises to 100%. Interdiffusion coefficients were obtained from the Auger profiles based on the concentration gradient at the Au-Cu interface (region (3)).Interdiffusion coefficients obtained from $\text{ΔG}\text{G}$ and from the Auger profiles agreed within a factor of 10 for all three methods of specimen preparation. Over the range 50–250°C the interdiffusion coefficient could be represented by $\text{D}\text{= 2.9 × 10}{}^{\mathrm{?3}}\text{exp(?1.21}\text{eV}\text{kT}\text{) cm}{}^2\text{s}{}^{\mathrm{?1}}$, giving 1.3 × 10^-19 cm² s^-1 at 100°C and 6.2 × 10^-15 cm² s^-1 at 250°C. These values fall within the range of extrapolations of previously published data obtained at higher temperatures.Auger profiles from a Cu ribbon which had been Au plated and stored for 18 years at room temperature prior to analysis were used to obtain an upper limit of 2 × 10^-20 cm² s^-1 for the interdiffusion coefficient at 25°C. Subsequent measurements of D? on this sample at 150–250°C were in agreement with values obtained for the other two types of CuAu specimens. This agreement leads to the conclusion that the room temperature interdiffusion coefficient in the other two types of samples is also less than 2 × 10^-20 cm² s^-1.     

Heat transfer to helium-I during different boiling regimes at high centrifugal accelerations

Heat transfer during nucleate and film boiling of helium and also the boiling crises up to relative accelerations of (1 ÷ 2) × 10³ have been investigated. The heat transfer surface was a flat copper heater. The heat transfer during nucleate boiling proved to be independent of the relative accelerations. For film boiling, it was found that $\text{α ～ η}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$. The dependence of the peak nucleate boiling heat flux and the minimum film boiling flux on the relative acceleration is non-monotonic.     

Properties of indium oxide films prepared by the reactive evaporation of indium

Indium oxide films with an electrical resistivity of about $\text{4 × 10}{}^{\mathrm{?4}}\text{Ω}\text{cm}$ and good optical quality were prepared by the reactive evaporation of pure indium in the presence of 10^?4 Torr of oxygen. The Auger electron spectrum of these films shows a deficiency of oxygen and corresponds to a composition which can be represented as In₂O_2.85. In the absence of foreign doping agents, the conduction electrons are provided by indium atoms which are adjacent to oxygen vacancies and act as a donor level. The electrical conductivity of the films is shown to be modulated by variations in the partial pressure of oxygen over the film which change the extent of the non-stoichiometry of the oxide by incorporation of oxygen into or extraction of oxygen from the film.     

Surface scattering effects in CdS thin films

A method, based upon the careful investigation of the dependence of the Hall coefficient on thickness, to determine the value of the mean surface scattering length λ is presented. Hall data presented for slowly deposited cadmium sulphide thin films indicate the relationship between λ and the carrier concentration. Data are also presented to exhibit the critical dependence of λ upon substrate temperature and deposition rate. The temperature dependence of the parameter λ/μ_b indicates the predicted $\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ relationship.     

Electrode-limited conduction in amorphous boron films I. D.C. measurements

The conduction mechanism in amorphous boron films sandwiched between plane gold electrodes has been investigated. The films, in the thickness range 3000–8000 Å, were obtained by the vacuum evaporation technique. The conduction process was examined in the temperature range 260–403 K with applied electric fields ranging from 10³ to 10⁵ V cm^-1. The temperature and field dependences of the current flowing through the insulator are understandable in terms of the thermal emission of charge carriers over the Schottky barrier of a blocking contact. The theory of this type of electrode-limited conduction, derived by Simmons, predicts a current-voltage relationship of the type $\text{J～}\text{exp}\text{(β V}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$. A good fit of the experimental J-V curves to this relationship is obtained. Furthermore, a set of parameters has been calculated: the height and the transmission coefficient of the potential barrier are respectively 0.43 eV and 10^-13, and the donor density within the insulator is equal to about 10²¹ cm^-3.     

Preparation of hexagonal potassium tungsten bronze thin films by thermal vacuum evaporation

$\text{K}{}_{\mathrm{x}}\text{WO}{}_{\mathrm{<mtext>3+</mtext><mtext>x</mtext><mtext>2</mtext>}}\text{(}\text{x}\text{= 0.3)}$ thin films have been prepared by the thermal vacuum evaporation technique. Depending on the substrate temperature during deposition, either amorphous or crystalline films could be obtained. X-ray diffraction patterns and pole-figure information revealed that fresh crystalline films deposited on a hot (about 400°C) substrate of indium-tin oxide on glass microscope slides had a preferred orientation, with the c-axis perpendicular to the surface of the film. SIMS depth profiles and RBS experiments were used to confirm the stoichiometry and uniformity of the chemical components in the thermally deposited films.     

Characterization of antimony-doped tin oxide films for solar cell applications

Transparent conducting undoped tin oxide (SnO₂) and antimony-doped tin oxide (ATO) films were deposited onto Pyrex glass and single-crystal silicon substrates using an inexpensive chemical vapour deposition system. SnCl₂ and SbCl₃ were used as the source reagents with oxygen and nitrogen respectively as the carrier gases. The deposition conditions were as follows: temperature, 350–500 °C; oxygen flow rate, 0.8–3.25 1 min^-1; nitrogen flow rate, 0–0.1 1 min^-1; deposition time, 5–20 min. The antimony concentration in the film and its physical properties were the same on both substrates. A figure of merit (Tr¹⁰/R_sh where Tr is the transmission at a particular wavelength and R_sh is the sheet resistance) was used to compare the performance of these films. The maximum figure of merit for SnO₂ films $\text{(1.43 × 10}{}^{-3}\text{Ω}{}^{-1}\text{(}\text{Tr}\text{= 95\% and R}{}_{\mathrm{<mtext>sh</mtext>}}\text{= 420 Ω/□))}$ was obtained when they were deposited at 500 °C with oxygen at a flow rate of 1 1 min^-1. The sheet resistance of antimony-doped films is a minimum at 3 mol.% Sb and the transmission decreases as the antimony concentration increases. The maximum figure of merit obtained for ATO films was $\text{6.78 × 10}{}^{-3}\text{Ω}{}^{-1}\text{(}\text{Tr}\text{= 90.6\% and R}{}_{\mathrm{<mtext>sh</mtext>}}\text{= 55 Ω/□)}$ for an antimony content of 3 mol.% and a nitrogen flow rate of 0.07 1 min^-1. These results are explained theoretically and are compared with those reported by other workers.     

Preparation of superconducting LiTi2O4 thin films

Superconducting LiTi₂O₄ thin films were prepared for the first time by the r.f. magnetron sputtering method and subsequent heat treatment. Their superconducting transition temperatures are 10.9–11.5 K, close to the transition temperatures of samples prepared by sintering or metling. Uniform films shows metallic conduction and have a resistivity of $\text{(4.3?8.8) × 10}{}^{-4}\text{Ω}\text{cm at}\text{15}\text{K}$ and a superconducting critical current density of 1.2 × 10⁴ A cm^-2 at 4.2 K. It was also found that the films are stable in an argon gas atmosphere.     

Application of flat dc-thin film SQUID's and technique for biomagnetic measurements

An improved flat dc-thin film SQUID with Dayem bridges has been used for the measurement of the magnetic fields of human heart and skeletal muscles. Using an antenna in form of superconducting asymmetric second derivative gradiometer a sensitivity to magnetic fields of $\text{1 × 10}{}^{\mathrm{?12}}\text{T}\text{Hz}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$ could be reached. The main features of measurement and some results are presented.     

Proton conduction in zeolites

Protonic conduction in zeolites is optimized. The approach is based on a vehicle-mechanism for the transport process. The parameters controlling protonic conduction are discussed. Fully hydrated “NH₄-zeolite A” has a room temperature conductivity of $\text{2×10}{}^{\mathrm{?3}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$. The material was successfully used in oxygen concentration cells (e.g. MnO₂/NH₄-zeolite A/Zn).     

Conductivite electrique et spectres de diffusion raman des verres mixtes AgPO3 − MI2 AVEC M = Cd,Hg, Pb. Correlation entre conductivite et structure

The glass-forming regions in the AgPO₃ ? MI₂ systems with M = Cd,Pb,Hg were determined. Electrical conductivity measurements and Raman spectra were carried out. A maximum conductivity value of $\text{10}{}^{\mathrm{?2}}\text{(Ω}\text{cm}\text{)}{}^{\mathrm{?1}}$ at 25°C is obtained for a mole fraction of 0,19 in PbI₂ or in CdI₂, whereas a value of $\text{3×10}{}^{\mathrm{?5}}\text{(Ω}\text{cm}\text{)}{}^{\mathrm{?1}}$ at 25°C is found for a mole fraction of 0,5 in HgI₂. The conductivity results and Raman spectra are examined and compared with those of AgPO₃ ? AgI. An exchange between Ag⁺ and M²⁺ ions is proposed leading to AgI species in AgPO₃ ? CdI₂ and AgPO₃ ? PbI₂ glasses. It could explain the high conductivity values obtained and the similarities observed in Raman spectra.     

Adatoms of indium on Si(111) surfaces: Application of reflection high energy electron diffraction to desorption experiments

An attempt is made to derive thermodynamic quantities which characterize the initial stages of film growth using reflection high energy electron diffraction. Critical temperatures for the appearance of superstructures (√3 × √3, √31 × √31 and 4 × 1) are determined for Si(111) surfaces which were bombarded with constant-flux molecular beams of indium (J = (0.05?3.5) × 10^-2 monolayers s^-1). Equilibrium between adsorption and desorption was observed at temperatures above 450 °C. From the J dependence of the critical temperatures, the sojourn time of indium adatoms on Si(111) 7 × 7 is estimated to be $\text{τ}{}_7\text{(T) = 9 × 10}{}^{-13}\text{exp}\text{(}\text{238}\text{kJ mol}{}^{-1}\text{RT}\text{)s}$.