Cubic forms in the surface morphology of CdS evaporated films

CdS films were grown by vacuum evaporation onto muscovite mica substrates. The surface structure of the films was investigated by electron microscopy, electron diffraction and X-ray diffraction. Growth structures typical of cubic symmetry have been observed, and those of the wurtzite-sphalerite and sphalerite-wurtzite transitions are also described. A discussion of experimental results in terms of the nucleation mechanism is given.     

Effect of annealing on the electrical and optical properties of electron beam evaporated ZnO thin films

Zinc oxide thin films have been grown on (100)-oriented silicon substrate at a temperature of 100 °C by reactive e-beam evaporation. Structural, electrical and optical characteristics have been compared before and after annealing in air by measurements of X-ray diffraction, real and imaginary parts of the dielectric coefficient, refractive index and electrical resistivity. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented with a full width at half maximum (FWMH) lower than 0.5°. The electrical resistivity increases from 10⁻² Ω cm to reach a value about 10⁹ Ω cm after annealing at 750 °C. The FWHM decreases after annealing treatment, which proves the crystal quality improvement. Ellipsometer measurements show the improvement of the refractive index and the real dielectric coefficient after annealing treatment at 750 °C of the ZnO films evaporated by electron beam. Atomic force microscopy shows that the surfaces of the electron beam evaporated ZnO are relatively smooth. Finally, a comparative study on structural and optical properties of the electron beam evaporated ZnO and the rf magnetron deposited one is discussed.     

Epitaxial growth and structure of CdS films evaporated onto Ge

CdS evaporated in vacuum grew epitaxially at all substrate temperatures from 300 to 500° C on (100), (110) and (111) surfaces of germanium. On (100) substrates the CdS grew with the sphalerite structure in parallel orientation to the substrate. Films grown throughout the epitaxial range of temperature gave diffraction patterns that contained no satellite spots. They all contained 111 streaking, however. The films were therefore free of threedimensional defects but contained a high density of {111} planar defects. On the (110) substrates the CdS grew with the sphalerite structure in parallel orientation for substrate temperatures below about 370° C and the diffraction patterns of these films were free of satellite spots but contained 111 streaks of low intensity. In the diffraction patterns of the films grown above about 370° C doubling of the spots appeared and a domain structure was observed in the micrographs. This was due to the occurrence of a domain-form phase transformation of the sphalerite structure. On the (111) substrates the CdS grew with the wurtzite structure in (0001) orientation. No satellite spots or streaks appeared in the diffraction patterns of these films. Moiré fringes were seen in the micrographs of both (100) and (111) substrate specimens.     

Resistivity study of the annealing kinetics of thin evaporated gold films

Thin gold films with thicknesses ranging between 70 and 1200 Å, formed by condensation onto Pyrex glass substrates at 273 K, have been studied in an ultrahigh vacuum system.Experimental data are given for the effect of annealing on film resistance. A kinetic analysis of isothermal annealing at 273 and 373 K has shown that resistance decay is a first order process that can be attributed to the random diffusion of vacancies to fixed sinks at grain boundaries and the free surface of the film. The activation free energy for defect migration was approximately 0.82 eV at 273 K.     

Effect of thermal annealing on the microstructure and morphology of erbium films

The effects of thermal annealing on the microstructure and morphology of erbium films were investigated by X-ray diffraction and scanning electron microscopy. All the erbium films were fabricated by electron-beam vapor deposition. The columnar grain sizes of as-received erbium films increased with the substrate temperatures and were enlarged by the coalescence and migration of grains during the high temperature annealing. The intrinsic stresses of erbium films, fabricated at a low substrate temperature (200 °C), were relaxed accompanied with the appearance of cracks on the films surface. The films deposited at 200 °C had (002) preferred orientation, and the film deposited at 450 °C had mixed (100) and (101) texture. The peak positions and the full width at half maximum of (100), (002), and (101) diffraction lines of erbium shift towards higher angles and sharply decrease during the annealing process, indicating that the stress inside the film was relaxed.     

Effect of thermal treatment on some properties of electrodeposited CdS thin films

An analysis of the influence of the temperature of thermal treatment on the properties of electrodeposited thin films of CdS has been carried out. The transition from cubic to hexagonal phase, and the changes of grain size and resistivity are studied.     

Effect of annealing on cathodoluminescence of synthetic zincite single crystals

We have studied the effect of annealing on the luminescent properties of zincite single crystals grown from hydrothermal solutions. Annealing in the temperature range of 400–700°C increases the edge cathodoluminescence (CL) intensity in zincite. At the same time, raising the annealing temperature from 800 to 1100°C leads to quenching of the edge emission and increases the intensity of the green band. In addition, annealing leads to broadening of the edge luminescence band and shifts it to lower energies. In contrast, annealing shifts the impurity band to higher energies. The observed changes in the CL behavior of zincite are tentatively interpreted in terms of the temperature effect on the concentration of structural defects, in particular, oxygen vacancies and their complexes.     

Effect of vacuum and H2S annealing on the electrical properties of CdS thin films

Polycrystalline CdS films were grown on to glass substrates kept at room temperature using a resistive heating technique. Films grown from the same batch were annealed in vacuum and H₂S vapour at 300 and 400° C for various periods up to 2 h. D.C. conductivity studies were made on these films in the temperature range 77 to 300 K. It was found that the d.c. conductivity decreases with vacuum and H₂S annealing; however, decrease is more significant in the latter films. X-ray diffraction studies were also carried out on these films.     

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.     

The influence of annealing on the resistivity and the thermoelectric power of evaporated palladium films

Palladium films in the thickness range from 5 to 60 nm were evaporated at 80 K and annealed at various temperatures up to 440 K. The resistivity and the thermoelectric power of the films were measured as functions of the thickness, the annealing temperature and the measuring temperature. It is necessary to use annealing temperatures as high as 400–440 K in order to obtain films in which the resistivity $\text{(?}{}_0\text{(280}\text{K}\text{) = 11.5 μΩ}\text{cm}\text{)}$ and the thermoelectric power (S₀(280 K) = ?9.3 μV K^?1) approach, when extrapolated to infinite thickness, the values of well-ordered bulk palladium (? = 10.03 μΩ cm, S = ?9.30 > μV K^?1 at 280 K).     

Structural transformation of dip coated CdS thin films during annealing

The present paper discusses structural transformation of CdS thin films during annealing and the consequent changes in their optical properties. CdS thin films are grown by the chemical bath deposition technique. The optical band gap is found to reduce on annealing and the change is attributed to the structural transformation of CdS from cubic to hexagonal phase. This revised version was published online in November 2006 with corrections to the Cover Date.     

On the structural changes during thermal oxidation of evaporated Zn thin films

Metallic Zn thin films (d = 200 nm-500 nm) were deposited in vacuum onto unheated glass substrate by quasi-closed volume technique at a source temperature of 723 K. Sets of samples simultaneously deposited on horizontally and vertically arranged substrates were prepared. The as-deposited Zn films were heated under ambient atmosphere at various temperatures ranged between 300 K and 650 K. By XRD and AFM techniques, the microstructural characteristics and their changes during Zn films heating were investigated. The influence of the deposition conditions on the structural changes during the oxidation process is also discussed.     

Effect of rapid thermal annealing on the crystal quality and the piezoelectric response of polycrystalline AlN films

This work analyzes the effect of post-deposition rapid thermal annealing (RTA) on the crystal quality and the piezoelectric response of sputtered polycrystalline aluminium nitride (AlN) thin films. AlN films with mixed crystal texture were not significantly affected by RTA processing. However, in films exhibiting clear c-axis preferred orientation, the annealing produced a crystallization process, characterized by an increase in the grain size of the original crystallites, the growth of new small grains, and the reduction of defects. The improvement in the crystal quality was more evident in highly textured c-axis oriented films. However, the enhanced crystal quality of the films due to RTA was not accompanied by a significant improvement in the piezoelectric response. This is attributed to the presence of grains with opposite polarities that could not be rearranged through the RTA treatment.     

Effect of CdCl2 annealing treatment on thin CdS films prepared by chemical bath deposition

In order to study the CdS recrystallization mechanism, a comparative study was carried out on thin films prepared by chemical bath deposition. The CdS films were annealed in air with or without a CdCl₂ coating layer. In-situ Raman spectra obtained during the annealing showed that both the air- and the CdCl₂-annealing did not cause rearrangement of the neighboring atoms in the CdS clusters below ~ 300 °C. CdS thin film was partially oxidated to CdO and CdSO₄ on the cluster surface when annealed in air. The oxides and the sulfur stoichiometric deficiency prevented the clusters to coalesce at higher temperatures. Coating thin CdS film with a thin CdCl₂ layer protected it from oxidation during annealing in air and promoted formation of Cl_S and V_Cd point defects in CdS. The anti-oxidation was attributed to the incorporation of a significant amount of Cl into CdS to form the Cl_S, which prevented the oxygen in-diffusion and chemical bonding during the annealing. The anti-oxidation at the CdS nano-crystalline surface and the point defects formed in the CdS promoted coalescence of the neighboring clusters without the need of long-range redistribution of the atoms. Large CdS grains with good crystalline quality formed through recrystallization during the CdCl₂ heat treatment, which provided the solid basis for the subsequent CdTe growth and high efficient CdS/CdTe solar cell fabrication.     

Effect of annealing on the reflectivity of silver films

Changes in the reflectivity of silver thin films produced by annealing at various temperatures are studied. Comparisons are made between the effects of annealing in air and in vacuum. Results are explained on the basis of hillock growth on the films.