Effect of annealing on structural,optical and electrical properties of pulse electrodeposited tin sulfide films

Polycrystalline tin sulfide (SnS) thin films were grown on conducting glass substrates by pulse electrodeposition. The effect of annealing on the physical properties such as structure, morphology, optical, and opto-electronic properties were evaluated to understand the effect of post-deposition treatment for SnS films. Annealing at temperatures higher than 250 °°C resulted in the formation of SnS₂ as a second phase, however, no significant grain growth or morphological changes were observed for films after annealing at 350 °C. A small change in band gap of 0.1 eV observed for films annealed at 350 °C was interpreted as due to the formation of SnS₂ rather than due to morphological changes. This interpretation was supported by X-ray diffractometry, scanning electron microscopy, and Raman spectral data. The electric conduction in the films is controlled by three shallow trap levels with activation energies 0.1, 0.05, and 0.03 eV. The trap with energy 0.03 eV disappeared after annealing at higher temperature, however, the other two traps were unaffected by annealing.     

On the electrical and optical properties of oxide nanolayers produced by the thermal oxidation of metal tin

Thin SnO_2–x layers, 30 nm in thickness, are produced by the thermal oxidation of metal tin nanolayers at a temperature of 450–750°C. The electrical and optical properties of the layers are studied. During the thermal oxidation of tin nanolayers, an unsteady variation in their conductivity is observed. For the oxide films produced at 450 and 550°C, an absorption band at 340 nm (3.65 eV) is detected in the optical spectra. The conductivity-activation energy is determined for samples oxidized to different degrees. On the basis of experimental data and the data reported in publications, an oxidation mechanism controlling the properties of Sn nanolayers is proposed.     

Effects of Ga concentration on structural and electrical properties of screen printed-CIGS absorber layers on polyethylene terephthalate

Copper indium gallium diselenide (CIGS) films were deposited as an absorber layer on polyethylene terephthalate (PET) substrates by a screen printing technique using CIGS ink with a Ga content ranging from 0.3 to 0.6. The melting point of PET substrate is 254.9 °C; the average transmission in the visible (400 nm–800 nm) for PET substrates is greater than 85%. Effects of Ga content of the CIGS absorber layer on structural and electrical properties of the CIGS films were studied. The lattice parameters, a and c for all CIGS films were decreased with increasing Ga content. At room temperature, Hall mobility and charge-carrier concentration of the CIGS films varies from 97.2 to 2.69 cm² V⁻¹ s⁻¹ and 9.98×10¹⁶ to 3.23×10¹⁸ cm⁻³, respectively.     

Texture of electrodeposited tin layers and its influence on their corrosion behavior

Differences in the degree of corrosion of pure thin tin films electrodeposited on copper substrates were investigated in dependence on the layer thickness and the texture of the tin layers. The change of the preferred orientation of the tin layer deposited by applying different current densities was analyzed using X-ray diffraction. A graphical evaluation was used to determine the degree of corrosion after sample exposition to NaCl contaminations and humidity. Results show that a preferred orientation along the lattice planes (3 2 1) and (2 2 0) enhances the corrosion resistance of the tin layer by about one order of magnitude compared to a non-textured sample based on the corroded area. In contrast, a texture along (1 0 1) and (1 1 2) accelerates the oxidation of tin by a factor of about three to four compared with a randomly orientated specimen. The corrosion dependence on the preferred orientation decreases with increasing layer thickness. Moreover, scanning electron micrographs show no effect to the size of the tin grains on variations of the current density. In summary, changes in the process parameters of the electrodeposition lead to a variation of texture and thus modify the chemical and corrosion properties of the resulting tin layers. Consequently reliability properties like solderability or whisker growth in further applications depend on these parameters.     

Influence of the fabrication conditions of polymorphous silicon films on their structural, electrical and optical properties

The structural, optical, and photoelectric properties of polymorphous silicon films produced by plasma-enhanced chemical vapor deposition from a mixture of monosilane and hydrogen at high pressure are studied. Variations in the pressure of the gas mixture used for film production barely change the Raman spectra of the films, but induce changes in the photoconductivity and in the absorption spectrum obtained by the constant-photocurrent technique. The experimentally observed change in the optical and photoelectric parameters of the films is attributed to some structural changes induced in the films by variations in the deposition parameters.     

Passivation effect on optical and electrical properties of molecular beam epitaxy-grown HgCdTe/CdTe/Si layers

The effects of passivation with two different passivants, ZnS and CdTe, and two different passivation techniques, physical vapor deposition (PVD) and molecular beam epitaxy (MBE), were quantified in terms of the minority carrier lifetime and extracted surface recombination velocity on both MBE-grown medium-wavelength ir (MWIR) and long-wavelength ir HgCdTe samples. A gradual increment of the minority carrier lifetime was reported as the passivation technique was changed from PVD ZnS to PVD CdTe, and finally to MBE CdTe, especially at low temperatures. A corresponding reduction in the extracted surface recombination velocity in the same order was also reported for the first time. Initial data on the 1/f noise values of as-grown MWIR samples showed a reduction of two orders of noise power after 1200-Å ZnS deposition.     

The effect of neutron irradiation and annealing temperature on the electrical properties and lattice constant of epitaxial gallium nitride layers

Effect of irradiation with high reactor-neutron fluences (Φ = 1.5 × 10¹⁷-8 × 10¹⁹ cm⁻²) and subsequent heat treatments in the temperature range 100–1000°C on the electrical properties and lattice constant of epitaxial GaN layers grown on an Al₂O₃ substrate is considered. It is shown that, with the neutron fluence increasing to (1–2) × 10¹⁸ cm⁻², the resistivity of the material grows to values of about 10¹⁰ Ω cm because of the formation of radiation defects, and, with the fluence raised further, the resistivity passes through a maximum and then decreases to 2 × 10⁶ Ω cm at 300 K, which is accounted for by the appearance of a hopping conductivity via deep defects in the overlapping outer parts of disordered regions. With the neutron fluence raised to 8 × 10¹⁹ cm⁻², the lattice constant c increases by 0.38% at a nearly unchanged parameter a. Heat treatment of irradiated samples at temperatures as high as 1000°C does not fully restore the lattice constant and the electrical parameters of the material.     

Structural properties and electrical behaviour of thin silicon oxynitride layers

Thin SiO₂ and SiO_xN_y layers were grown on silicon using Rapid Thermal Processing (RTP) in either O₂ or N₂O ambient. Subsequent annealing or nitridation was performed in order to improve the electrical stability. The composition of the films, in particular the incorporation of nitrogen and hydrogen, has been studied. We obtained the distribution of states at the Si/insulator interface through the evaluation of CV measurements and investigated the charge trapping in the layers analysing the voltage–time behaviour during Fowler–Nordheim constant current injection. Furthermore, assuming a trap assisted tunneling mechanism, the influence of near interface trap states on the current voltage characteristic was used to derive an effective insulator state distribution.     

Substrate temperature effect on structural,optical and electrical properties of vacuum evaporated SnO2 thin films

Tin oxide (SnO₂) thin films were deposited on glass substrates by thermal evaporation at different substrate temperatures. Increasing substrate temperature (T_s) from 250 to 450 °C reduced resistivity of SnO₂ thin films from 18×10⁻⁴ to 4×10⁻⁴▒ Ω ▒cm. Further increase of temperature up to 550 °C had no effect on the resistivity. For films prepared at 450 °C, high transparency (91.5%) over the visible wavelength region of spectrum was obtained. Refractive index and porosity of the layers were also calculated. A direct band gap at different substrate temperatures is in the range of 3.55−3.77 eV. X-ray diffraction (XRD) results suggested that all films were amorphous in structure at lower substrate temperatures, while crystalline SnO₂ films were obtained at higher temperatures. Scanning electron microscopy images showed that the grain size and crystallinity of films depend on the substrate temperature. SnO₂ films prepared at 550 °C have a very smooth surface with an RMS roughness of 0.38 nm.     

Annealing temperature effect on electrical and structural properties of Cu/Au Schottky contacts to n-type GaN

Schottky contacts were fabricated on n-type GaN using a Cu/Au metallization scheme, and the electrical and structural properties have been investigated as a function of annealing temperature by current-voltage (I-V), capacitance-voltage (C-V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements. The extracted Schottky barrier height of the as-deposited contact was found to be 0.69 eV (I-V) and 0.77 eV (C-V), respectively. However, the Schottky barrier height of the Cu/Au contact slightly increases to 0.77 eV (I-V) and 1.18 eV (C-V) when the contact was annealed at 300 °C for 1 min. It is shown that the Schottky barrier height decreases to 0.73 eV (I-V) and 0.99 eV (C-V), 0.56 eV (I-V) and 0.87 eV (C-V) after annealing at 400 °C and 500 °C for 1 min in N₂ atmosphere. Norde method was also used to extract the barrier height of Cu/Au contacts and the values are 0.69 eV for the as-deposited, 0.76 eV at 300 °C, 0.71 eV at 400 °C and 0.56 eV at 500 °C which are in good agreement with those obtained by the I-V method. Based on Auger electron spectroscopy and X-ray diffraction results, the formation of nitride phases at the Cu/Au/n-GaN interface could be the reason for the degradation of Schottky barrier height upon annealing at 500 °C.     

Influence of thermal annealing on electrical and optical properties of indium tin oxide thin films

Transparent conducting indium tin oxide (ITO) thin films with the thickness of 300 nm were deposited on quartz substrates via electron beam evaporation, and five of them post-annealed in air atmosphere for 10 min at five selected temperature points from 200 °C to 600 °C, respectively. An UV–vis spectrophotometer and Hall measurement system were adopted to characterize the ITO thin films. Influence of thermal annealing in air atmosphere on electrical and optical properties was investigated in detail. The sheet resistance reached the minimum of 6.67 Ω/sq after annealed at 300 °C. It increased dramatically at even higher annealing temperature. The mean transmittance over the range from 400 nm to 800 nm reached the maximum of 89.03% after annealed at 400 °C, and the figure of merit reached the maximum of 17.79 (Unit: 10⁻³ Ω⁻¹) under the same annealing condition. With the annealing temperature increased from 400 °C to 600 °C, the variations of transmittance were negligible, but the figure of merit decreased significantly due to the deterioration of electrical conductivity. With increasing the annealing temperature, the absorption edge shifted towards longer wavelength. It could be explained on the basis of Burstein–Moss shift. The values of optical band gap varied in the range of 3.866–4.392 eV.     

Role of substrate in electrical properties of GaAs implanted layers

The variation of implantation efficiency in different semi-insulating GaAs materials is shown to be correlated with he purity of the starting substrate, i.e. its Cr concentration and more especially its value of ND?NA (shallow levels). This last value appears to be a key parameter in the electrical properties of implanted layers.     

Effect of tin content on the electrical and optical properties of sprayed silver sulfide semiconductor thin films

Silver sulfide (Ag₂S) thin films have been deposited on glass substrates by t spray pyrolysis using an aqueous solution which contains silver acetate and thiourea as precursors. The depositions were carried out at a substrate temperature of 250 °C. Structural studies by means of X-ray diffraction show that all tin (Sn)-doped Ag₂S thin films crystallized in a monoclinic space group with noticeable changes in the crystallites' orientation. The discussion of some structural calculated constants has been made with Sn doping in terms of microhardness measurements. Moreover, the optical analysis via the transmittance, reflectance as well as the photocurrent reveals that the direct band gap energy (E_gd) decreases (E_gd varies from 2.34 to 2.16 eV) and the indirect band gap energy (E_gi) increases (E_gi varies from 0.98 to 1.09 eV) slightly as a function of Sn content. Electrical study shows that Sn doping changes the electrical conductivity and proves the thermal activation of electrical conduction.     

The effect of substrate misorientation on the optical, structural, and electrical properties of GaN grown on sapphire by MOCVD

We report the growth and characterization of unintentionally doped GaN on both exact and vicinal (0001) sapphire substrates. The GaN heteroepitaxial layers are grown by metalorganic chemical vapor deposition on c-plane A1₂O₃ substrates either on-axis or intentionally misoriented 2° toward the a-plane (1120) or 5 or 9° toward the m-plane (10 10). The samples are characterized by 300K photoluminescence, cathodoluminescence, and Hall-effect measurements as well as by triple-axis x-ray diffractometry to determine the effect of the misorientation on the optical, electrical, and structural properties of heteroepitaxial undoped GaN. Ten different sample sets are studied. The data reveal enhanced photo-luminescence properties, increased electron mobility, a reduced n-type background carrier concentration, and a somewhat degraded surface morphology and crystalline quality for the misoriented samples compared to the on-axis samples.     

Infrared study of the effect of some solvents on the structural properties of soybean proteins

The effect of three groups of solvents classified according to their water miscibility on soybean proteins at 80°C and 100°C was investigated by following the changes in their infrared spectra. The results showed that, for immiscible solvents, the values of the absorbances ratios $$\frac{{A 1660 cm^{ - 1} }}{{A 2950 cm^{ - 1} }}and\frac{{A 1530 cm^{ - 1} }}{{A 2950 cm^{ - 1} }}$$ depend on the nature of the solvents used and the temperature of treatment. It was, also, found that these absorbances ratios are influenced by number of carbon atoms, branching and dipole moment of the solvents. Furthermore, the results revealed that these ratios are temperature dependent.     

锡后处理对锡镀层性能的影响

分别测试了纯锡镀层经钝化及金属保护剂处理后的孔隙率、防变色能力、可焊、回流焊性能及抑制锡须生长情况。试验结果表明:对纯锡层采用钝化和金属保护剂处理均能有效降低镀层的孔隙率,提高镀层的防变色能力。金属保护剂处理能有效防止锡层的氧化,延长产品的储存寿命,对焊接性能无影响,同时能有效抑制锡须生长;钝化处理降低了锡镀层的焊接性能,对抑制锡须生长作用不明显。     

Effects of H2/NH3 flow-rate ratio on the luminescent, structural, and electrical properties of GaN epitaxial layers grown by MOCVD

GaN epitaxial layers were grown on sapphire substrates in a separate-flow reactor by metalorganic chemical vapor deposition. The flow-rate ratio of H₂ on the upper stream to NH₃ on the bottom stream is varied from 0.5 to 2. The growth condition and characterization of the GaN epitaxial layers are investigated in detail. The H₂ flow rate of the upper stream strongly affects the reactant gas flow pattern near the substrate surface and thus influences the quality of epitaxial layers. At the optimum H₂/NH₃ flow ratio of 1.0, we can obtain a good quality of GaN epitaxial layers which exhibit a strong near band-edge emis-sion in the 20 K photoluminescence (PL), a full width at half maximum of 66 meV for the 300 K PL, an electron mobility of 266 cm²/V-s and concentration of 1 × 10¹⁸ cm⁻³ at 300 K.     

Comparative study between electrical, optical and structural properties of annealed heavily carbon doped GaAs

Heavily C-doped GaAs epilayers have been grown by atmospheric pressure metalorganic vapor phase epitaxy with hole concentration ranging from 2×10¹⁹ to 1.6×10²⁰ cm⁻³. In order to study the stability of C acceptors over this range, the films have been annealed at 810 °C for 10 min under two mixture gas AsH₃+H₂ or only N₂. Annealing of the layers resulted in a decrease in carrier concentration, carrier mobility and lattice mismatch with undoped GaAs. The lattice matching conditions of C-doped GaAs layers were systematically investigated by using X-ray high-resolution diffraction space mapping. The comparison between electrical and structural before and after annealing of layers properties indicates that the simultaneous decrease of carrier concentrations, Hall mobility and mismatch is probably related to an increase of compensation. Basing on a theoretical calculation of mobility as a function of hole concentration and Vegard's law, we estimate that the compensation comes from the formation of (C-C)⁺_[100] interstitial couples. This fact does not exclude definitively the possibility of the formation of other species such as H-C_As especially for hole concentration lower than 5×10¹⁹ cm⁻³. An annealing under AsH₃+H₂ ameliorates the crystalline properties contrarily to an annealing under N₂. The optical properties have been investigated using Raman spectroscopy. Two main Raman features are observed before and after annealing of the layers: the longitudinal-optic (LO) phonon mode and the coupled plasmon-LO phonon (LOPC). As for as grown layers, the intensity ratio I_LOPC/I_LO between the intensity of LOPC peak and the LO peak increases by increasing the hole concentration. This ratio is about 1 after an annealing of layers under AsH₃+H₂. An unusual change of I_LOPC/I_LO ratio is observed in samples annealed under N₂. Indeed, for high doping (∼10²⁰ cm⁻³) the ratio I_LOPC/I_LO<1 and for relatively low doping (∼2×10¹⁹ cm⁻³) the ratio I_LOPC/I_LO>1. This behaviour is probably related to the high sensibility of Raman measurement not only to the hole concentration change but also to the surface quality.     

Substrate temperature effect on the photophysical and microstructural properties of fluorine-doped tin oxide nanoparticles

Transparent conducting oxide of fluorine-doped tin oxide (FTO) thin films was deposited from chemical solutions of tin chloride and ammonium fluoride using streaming process for electroless and electrochemical deposition (SPEED) at substrate temperature 450, 500, and 530 ℃ respectively. The effect of substrate temperatures on the microstructural properties such as crystallite size, dislocation density, micro strain, volume of the unit cell, volume of the nanoparticles, number of the unit cell, bond length and the lattice constants were examined using XRD technique. Only reflections from (110) and (200) planes of tetragonal SnO₂ crystal structure were obvious. The peaks are relatively weak indicating that the deposited materials constitute grains in the nano dimension. Hall measurements, which were done using van der Pauw technique, showed that the FTO films are n-type semiconductors. The most favorable electrical values were achieved for the film grown at 530 ℃ with low resistivity of 7.64×10^-4Ω·cm and Hall mobility of -9.92 cm²/(V·s).     

Effect of fullerene doping on the electrical properties of P3HT/PCBM layers

Poly (3-hexylthiophene-2, 5-diyl) (P3HT) and its blend with Phenyl-C₆₁-Butyric acid-Methyl-Ester (PCBM) and fullerene (C₆₀) thin films were prepared and their electrical properties for memory applications were studied. Due to doping, a sharp decrease in the resistance for a P3HT:PCBM:C₆₀ device was observed at around 70 °C which makes it useful for thermal switching applications. Addition of C₆₀ to P3HT:PCBM blend gave a high value for R_RESET/R_SET in thermal switching. For bias switching, threshold voltage reduces to 1.4 V from 25 V with the addition of C₆₀ to P3HT layer.