Lead Sulfide Films Research Articles

Optical and electrical properties of Pbs+In thin films subjected to thermal processing

Indium thin film (∼20 nm) deposited on intrinsic lead sulfide films leads to the formation of an n-type composite layer when annealed in nitrogen atmosphere at 350–400°C. The formation of metallic lead and indium oxide is observed in the X-ray diffraction patterns of the films. The dark conductivity of the PbS+In films after nitrogen annealing at 400°C attains a value of 500 Ω −1 cm −1, which is higher by five orders of magnitude compared with as-prepared PbS films. Modifications in the optical and electrical properties of PbS+In films after annealing are attributed to the presence of metallic lead and indium oxide in the films.

New Heterostructures n-PbS/n-ZnSe: Long-Term Stability of Electrical Characteristics

The long-term stability of electrical parameters had been investigated for heterostructures based on lead sulphide films and zinc selenide during 3.5 years samples storage at normal ambient conditions. In order to clarify the time stability of electrical properties characterized the examined heterostructures the investigations of current-voltage and capacitance-voltage dependencies were performed. It was found that the heterostructures characterized by the carrier concentration of ZnSe substrate in range of (1.5-3.5)x1017 cm-3 manifested more stable current-voltage behavior than the heterostructures with the lower carrier concentration of the ZnSe substrate.

RESPONSIVITY IMPROVEMENT OF PHOTOCONDUCTIVE INFRARED DETECTROS

Lead Sulfide (PbS) in thin film form is used in many applications as ar, infrared detector . In this work amorphous lead sulfide films was prepared using different thermal evaporation techniques . Electrical and structural measurements were done upon the as grown films. In order to enhance the electrical and structural characteristics, several heat treatment processes were done at temperatures of 250., 350, 420 °C . This study showed a great improvement in the detector responsivity due to the performed heat treatments which can be simulated in other types of detector materials.

The Development of Infrared Photosensitive Material Based on Polycrystalline PbS Films

AbstractPolycrystalline thin films of lead sulphide were deposited on glass substrates by the hot wall technique. The grain size varied from 100 to 500 A by varying the growth rate and the substrate temperature. The grain boundaries are assumed to influence the optoelectronic properties of polycrystalline films by generating potential energy relieves, estimated to reach 0.1 eV. We investigated the influence of the barrier height by introducing impurity atmospheres into the grain boundaries. Oxygen and indium were introduced into the films by diffusion from a gas phase. Conductivity was measured in the 80-300 K range. It rises with increasing temperature in oxygen doped films, indicating that conductivity is a thermal activation process. In the same time the conductivity of In doped PbS films decreases with temperature like in PbS single crystals. Photoconductivity was observed in films annealed in oxygen, which was significant up to room temperature. Carrier lifetime was found to decrease with rising temperature and be larger in films annealed in oxygen.A model is proposed to explain the optoelectronic behavior of the polycrystalline films. It is proposed that charge accumulation near grain boundaries set up potential barriers for free carriers. The barriers increase by oxygen and decreases by indium doping. The charge carriers generated by an illumination become spatially separated at grain boundaries. This separation retards their recombination and increases their lifetime, giving rise to persistent photoconductivity and potential high photosensitivity.

Electrodeposition of lead sulphide in acidic medium

Abstract Polycrystalline thin films of lead sulphide were electrodeposited on titanium, aluminium and stainless steel (SS) substrates at a constant potential of −0.7V vs. Ag|AgCl|(sat)KCl electrode using 1mM solutions of Pb(NO 3 ) 2 and Na 2 S 2 O 3 at pH 2.7, 2.8 and 2.9 Except at pH 2.9 (which also gave tetragonal PbS 2 ) all other pHs gave single phase PbS (fee). While deposition on Al gave a crystalline phase of PbS with very prominent (200) and (111) planes, that on SS substrate showed growth of the (200) plane only. Although the deposition of PbS on Ti was good. it showed (111) and (200) planes of low intensity compared to that on Al. Film thickness and grain size were found to be of the order of micrometres. The cyclic voltammetry of the film formation was studied in a potential range −1 to 0V (Ag|AgCl) followed by XRD, SEM and AFM analyses. The mechanism of growth is discussed.

The study of lead sulphide films. VI. Influence of oxidants on the chemically deposited PbS thin films

By treating the PbS films in H 2O 2 solution an increase of electrical resistance and photosensitivity (the last being about ten-fold greater) was observed. In the case of K 2S 2O 8, a similar phenomenon was ascertained, but with a very high electrical resistance and a lower photosensitivity. The presence of PbSO 4 in thin films was proved by IR spectroscopy. The SO 4 2− content varies within the range 15–26 wt.%. The PbS films obtained in the presence of oxidants are characterized by electrical resistances which increase with the quantity of oxidant added. The photosensitivity has a maximum of 0.035 mol l −1 H 2O 2. The IR spectrum shows the appearance of lead cyanamide PbCN 2 (13.1 wt.% in the sample with highest photosensitivity). The oxidation products and other detected impurities substantially influence the electrical and photoelectrical properties of PbS layers.

The study of lead sulfide films The behaviour at low-temperature thermal treatment

The influence of annealing temperature on the sheet electrical resistance in the dark ( R□d) and the photosensitivity ( S) of the chemically deposited PbS thin films (thickness, 0.12–0.20 μm) was studied. By thermal treatment in air at 75–150°C, the parameters were increased, but after keeping the samples on anhydrous CaCl 2 or P 2O 5, they decreased. The process is reversible and can be interpreted as a sorption/ desorption of H 2O vapours. The concentration of SO 4 2− ions in the annealed films as determined by spectrophotometric titration, was 76–200 μg cm −2. By X-ray diffraction analysis, an increase of the average crystallite size and a decrease of the microstrains were observed.

Optical properties of thin solid films of lead sulfide

The technique of electroless chemical deposition was used for preparation of thin solid films of lead sulfide (PbS). The thin solid PbS films were deposited on a glass substrate previously coated with a very thin layer of Cu2S. The optimal temperature of deposition was between 343 and 363 K. The thickness of these films was controlled by changing the concentration of the reaction solutions and the deposition time.The optical properties of these thin solid films of different thickness were determined by means of near infrared spectroscopy, Raman spectroscopy and visible spectroscopy.

Preparation of lead iodide films by iodination of chemically deposited lead sulphide films

A method of preparation of PbI 2 films by iodination of chemically deposited PbS films is described. The X-ray characterization of these films show that they are poly-crystalline in nature and the crystallites are preferentially oriented with c-axis perpendicular to the plane of the substrates. The analysis of the diffuse reflectance measurements performed on material scraped off the substrates yielded a forbidden energy gap of 2.34 eV in conformation with the results of pure PbI 2 powder. The transmittance spectra of these films, in the wavelength range 400 to 600 nm, revealed a characteristic strong absorption edge at about 510 nm and a hump at about 490 nm. On the basis of the changes in conductance of PbS film during iodine treatment a mechanism of iodination has been proposed.

Small-angle x-ray scattering and inhomogeneities of the electron density in polycrystalline and epitaxial PbS films

The dependence of the characteristics of the macro- and microporosity on the condensation temperature has been studied for condensation temperatures from 30 to 450°C by small-angle x-ray scattering, hydrostatic weighing, and low-temperature desorption of argon in polycrystalline and single-crystal lead sulfide films with thickness 3–5 μm condensed for normal incidence of the molecular beam on polycrystalline and single-crystal substrates. The porosity of the polycrystalline films is an order of magnitude greater than in the epitaxial films. In polycrystalline condensates, the pores are elongated and are oriented along the normal to the film. The pores in the epitaxial films have a platelet form with faces along the {100} planes and are parallel to the direction of growth of the condensate. At high substrate temperature (about 400°C), more nearly equiaxial pores, with additional {110} faces are formed, as a result of the plastic deformation of the condensate by thermal macrostresses.

3671. The structure and growth of thin films of lead sulphide condensed in vacuum on to amorphous substrates and their systematic dependence on film thickness, residual gas pressure and residual gas composition: S J Boichot, J Phys D: Appl Phys, 11 (4), 1978, 499–508

3671. The structure and growth of thin films of lead sulphide condensed in vacuum on to amorphous substrates and their systematic dependence on film thickness, residual gas pressure and residual gas composition: S J Boichot, J Phys D: Appl Phys, 11 (4), 1978, 499–508

The structure and growth of thin films of lead sulphide condensed in vacuum on to amorphous substrates and their systematic dependence on film thickness, residual gas pressure and residual gas composition

Surface structures at a series of thicknesses were determined by high energy electron diffraction at grazing incidence of the electron beam and in films up to 1000 AA thick by electron microscopy. Four distinct regions of crystal orientation as a function of film thickness and residual gas pressure are identified and discussed and the relationship between the angle of vapour incidence and the orientation axis is considered. The development of orientations as a consequence of surface atomic mobility, face development and subsequent twinning of the growing crystals is discussed and the influence of the residual gases on the growing films is also considered.

Selective absorption properties of lead sulfide–aluminum coatings as a function of lead sulfide thickness

The dependence of the absorptivity and emissivity of lead sulfide films on thickness was investigated. Theoretical calculations were made using the bulk–lead sulfide model. Reflectance measurements in the visible and infrared regions of the spectrum were made to determine absorptivity and emissivity values. Both the theoretical and experimental results predict optimum a/e values for the lead sulfide thickness range 300–800 Å.

Microstructure of lead sulfide films. (USSR): V I Birynlev and G P Tikhomirov, Optiko-Mekh Prom, No 6, 1974, 64 ( in Russian)

Microstructure of lead sulfide films. (USSR): V I Birynlev and G P Tikhomirov, Optiko-Mekh Prom, No 6, 1974, 64 ( in Russian)

Variation of the properties of chemically deposited lead sulfide film with the use of an oxidant

The structural, chemical, and photoelectronic properties are compared for three types of chemically deposited lead sulfide film. The film types differ in the use of an oxidant during the deposition. The films are grainy in structure and show a decrease in grain compaction as the concentration of the oxidant is increased. Nominal chemical composition, including the concentration of oxygen, is not significantly dependent on the use of the oxidant. Photosensitive films may be described in terms of sensitizing centers which are present only when an oxidant is used but which are not dependent solely on the presence of oxygen. The physical identification of the sensitizing centers has not been determined but may be associated with film structure.

538. Electrolytic photography on evaporated films of lead sulphide: L V Belyakov et al, Fiz Tekh Polup, 5 (7), 1971, 1466–1468 ( in Russian)

538. Electrolytic photography on evaporated films of lead sulphide: L V Belyakov et al, Fiz Tekh Polup, 5 (7), 1971, 1466–1468 ( in Russian)

Investigation of the oxidation of epitaxial lead sulphide films by means of LEED: An Tuan Khoang and G K Zyryanov, Uch Zap LGU, No 354, 1970, 96–98 ( in Russian)

The process of field-evaporation on a lanthanum hexaboride (LaB6) (001) plane was studied by atom-probe field ion microscopy (FIM) in the presence of hydrogen at cryogenic temperature. The results, obtained from mass spectra and layer-by-layer analyses, suggest that (1) the boron surface atoms react with the hydrogen gas atoms preferentially on the surface and many boron atoms field-evaporate as boron hydride ions with a holding voltage applied to the specimen, (2) a large part of the lanthanum surface atoms also form hydride ions induced by a pulse-voltage on the surface but they dissociate to La3+ ions and neutral H atoms immediately after their field-evaporation, and (3) the lanthanum surface atoms have a great contribution to a hydrogen gas ion image of the LaB6(001) plane.

A Chemical Method of Preparing Photoconducting Lead Sulphide Films

A Chemical Method of Preparing Photoconducting Lead Sulphide Films

585. Investigation of angular distribution of high photo-voltage in polycrystalline films of lead sulphide

585. Investigation of angular distribution of high photo-voltage in polycrystalline films of lead sulphide

289. Production of a photographic image by oxidizing-reducing reactions on thin films of lead sulphide and selenide: D N Goryachev et al, Fiz Tekh Poluprovod, 4 (8), Aug 1970, 1580–1581 ( in Russian)

289. Production of a photographic image by oxidizing-reducing reactions on thin films of lead sulphide and selenide: D N Goryachev et al, Fiz Tekh Poluprovod, 4 (8), Aug 1970, 1580–1581 ( in Russian)