Optical, structural and electrical properties of Mn doped tin oxide thin films

Mn doped SnO_x thin films have been fabricated by extended annealing of Mn/SnO₂ bilayers at 200°C in air for 110 h. The dopant concentration was varied by controlling the thickness of the metal layer. The overall thickness of the film was 115 nm with dopant concentration between 0 and 30 wt% of Mn. The films exhibit nanocrystalline size (10-20 nm) and presence of both SnO and SnO₂. The highest transmission observed in the films was 75% and the band gap varied between 2.7 and 3.4 eV. Significantly, it was observed that at a dopant concentration of ∼4 wt% the transmission in the films reached a minimum accompanied by a decrease in the optical band gap. At the same value of dopant concentration the resistivity also reached a peak. This behaviour appears to be a consequence of valence fluctuation in Sn between the 2+ and 4+ states. The transparent conductivity behaviour fits into a model that attributes it to the presence of Sn interstitials rather than oxygen vacancies alone in the presence of Sn^{2 +}.     

Metallic contacts to nitrogen and boron doped diamond-like carbon films

Hydrogenated diamond-like carbon (DLC) was deposited using a radio-frequency plasma-enhanced chemical vapor deposition method. Electrical properties of Al, Au, Ti, and Zr contacts to nitrogen and boron doped DLC films have been studied, and mechanisms of the observed current-voltage (I-V) characteristics are investigated. Linear I-V characteristics were observed for Au, Ti, and Zr contacts to both nitrogen and boron doped DLC films. A band structure model for metal-DLC contact is proposed to explain the observed ohmic contacts. Fermi level shifting at the surface of DLC films produces an ohmic resistive layer instead of a Schottky barrier for metal-DLC contacts. Al contacts to both nitrogen and boron doped DLC films show nonlinear I-V characteristics, which are attributed to a dielectric layer of carbide (Al₄C₃) instead of a Schottky barrier suggested by other groups. Inert elements such as Au and Pt, and transition metals such as Ti, Zr and W, which form conductive carbides, are considered good contacting metals for electrical studies of DLC films.     

Investigation of optical,structural and morphological properties of nanostructured boron doped TiO 2 thin films

Pure and different ratios (1, 3, 5, 7 and 10%) of boron doped TiO₂ thin films were grown on the glass substrate by using sol–gel dip coating method having some benefits such as basic and easy applicability compared to other thin film production methods. To investigate the effect of boron doped on the physical properties of TiO₂, structural, morphological and optical properties of growth thin films were examined. 1% boron-doping has no effect on optical properties of TiO₂ thin film; however, optical properties vary with > 1%. From X-ray diffraction spectra, it is seen that TiO₂ thin films together with doping of boron were formed along with TiB₂ hexagonal structure having (111) orientation, B₂O₃ cubic structure having (310) orientation, TiB_0·024O ₂ tetragonal structure having rutile phase (110) orientation and polycrystalline structures. From SEM images, it is seen that particles together with doping of boron have homogeneously distributed and held onto surface.     

Study of structural and optical properties of Ge doped ZnO films

The Ge doped ZnO films were deposited on quartz substrates by radio frequency magnetron sputtering. The effects of doping and substrate temperature on the structural and optical properties of the Ge doped ZnO films were investigated by means of X-ray diffraction (XRD), UV-visible transmission spectra, X-ray photoelectron spectroscopy and photoluminescence (PL) spectra. The XRD patterns showed that Zn₂GeO₄ phases were formed in the films. With the increase of substrate temperature the crystallization of Zn₂GeO₄ was improved, and that of ZnO phases turned worse, and no diffraction peak of ZnO was observed when the substrate temperature was 700 °C. Obvious ultraviolet (UV) light emission was found due to ZnO grains, and it was much stronger than that of un-doped ZnO films. The enhancement of UV light emission at about 380 nm may be caused by excitons which were formed at the interface between Zn₂GeO₄ and ZnO grains. In the visible region of the PL spectra, the green light emission peak of samples at about 512 nm was associated with defects in ZnO. A red shift of the green light emission peak was observed which can be explained by the fact that there is a luminescence center at about 548 nm taking the place of the defect emission of ZnO with the increase of substrate temperature. The red shift of the green light emission peak and the 548 nm green light emission peaks of the PL spectrum show that some Ge²⁺ should replace the Zn²⁺ positions during the Zn₂GeO₄ grains growth and form the Ge²⁺ luminescence centers in Zn₂GeO₄ grains.     

Grain boundary effect on the electrical properties of boron-doped polysilicon films

The effect of grain boundary width has been accounted for and a modified simple model of average carrier concentration is presented considering the transport mechanism of charge carriers by thermionic emission only. It is found that the electrical properties of polysilicon are very sensitive to doping concentration when the grain size is small and the effect of grain boundary width on electrical properties increases as the grain size decreases. The inclusion of grain boundary width in resistivity and mobility formulae also gives better results near the critical doping concentration. The proposed model gives better agreement between experimental data and theoretical results.     

Structural and optical properties of nitrogen doped ZnO films

Zinc oxide is getting an enormous attention due to its potential applications in a variety of fields such as optoelectronics, spintronics and sensors. The renewed interest in this wide band gap oxide semiconductor relies on its direct high energy gap (E_g ∼ 3.437 eV at low temperatures) and large exciton binding energy. However to reach the stage of device production the difficulty to produce in a reproducible way p-type doping must be overcome.In this study we discuss the structural and optical properties of ZnO films doped with nitrogen, a potential p-type dopant. The films were deposited by magnetron sputtering using different conditions and substrates. The composition and structural properties of the films were studied combining X-ray diffraction (XRD), Rutherford backscattering (RBS), and heavy ion elastic recoil detection analysis (HI-ERDA). The results show an improvement of the quality of the films deposited on sapphire with increasing radio-frequency (RF) power with a preferentially growth along the c-axis. The ERDA analysis reveals the presence of H in the films and a homogeneous composition over the entire thickness. The photoluminescence of annealed samples evidences an improvement on the optical quality as identified by the well structured near band edge recombination.     

用铝丝掺杂溅射ZnO薄膜的光电性能研究

本文采用射频磁控反应溅射法于常温下在硅片和玻璃基片上制备ZnO和掺铝ZnO薄膜,将铝丝置于ZnO靶材上共同溅射来达到掺杂的效果,利用不同长度的铝丝以获得不同的掺杂量。通过X射线衍射法对薄膜进行结构分析,利用紫外-可见分光光度计获得薄膜的透过率光谱,霍尔效应仪测量薄膜的电学性能。发现所制备的样品在可见光区域透过率达到80%以上,达到了透明膜的要求;掺Al后的ZnO膜电阻率最低达到了4.25×10-4Ω·cm;结构表征发现样品的(002)晶面有明显衍射峰。基于包络线方法通过透射谱拟合计算了薄膜样品的折射率和厚度。     

Electrical and structural properties of ortho-chloranil doped zinc phthalocyanine films

Electrical conductivity of evaporated zinc phthalocyanine (ZnPc) films, doped with orthochloranil (o-CA) molecules, is investigated. Benzoico-CA solution is introduced in the film and benzene is removed by vapourization afterwards. The film conductivity at first increased and then decreased with incremental doping. The maximum conductivity of the sample appeared at doping level × (=o-CA/ZnPc) 0.2 and is about 10³ times as large as that of the as-evaporated one. About a ten-fold further increase in the conductivity is obtained by the heat-treatment of 150 °C for 12 h. The conductivity change by doping is explained by taking into account thato-CA molecules behave not only as acceptors in the film but destructively for the film structure. The phase change of ZnPc by benzoic solution is also discussed.     

Annealing effect on structural, optical and electrical properties of pure and Mg doped tin oxide thin films

This study describes the effect of annealing at different temperatures (400–600 °C) on structural, optical and electrical behaviors of pure and Mg doped tin oxide thin films grown on the glass substrate by electron beam evaporation technique. The transformation of tetragonal to orthorhombic form due to annealing, introduced a change in the optical and electrical properties of pure and Mg doped tin oxide thin films. X-ray diffraction studies or analysis revealed the phase transformation and change in the crystalline size with increase in the annealing temperature. The morphology and roughness of the thin films were studied by Atomic force microscopy. Optical band gap increased with annealing temperature confirms the improvements of crystallinity. The quality of thin films transparency was investigated by UV/Vis-spectroscopy. Photoluminescence of pure and Mg doped tin oxide thin films shows two extra peaks one at 486 nm and other at 538 nm is due to the crystal defect created as a result of annealing temperature. These peaks became stronger and shifted to longer wavelength with increasing the annealing temperature. The complex plot (Nyquist plot) showed the data point laying on two semicircles and the resistance of grains and grain boundaries increases with the increase in annealing temperature for both pure and Mg doped tin oxide thin films.     

Correlated structural and electrical properties of thin manganese oxide films

In the present work, different crystalline Mn-oxide thin films (MnO, α-Mn₂O₃, and γ-Mn₂O₃) were prepared on glass and Si(P) substrates by evaporation of MnO₂ powder followed by annealing in air and in vacuum at different temperatures. The oxide films were characterised by methods of energy-dispersion X-ray fluorescence method (EDXRF), X-ray diffraction (XRD), and ultraviolet-visible (UV-VIS) optical spectroscopy. The samples for electrical study were constructed in the form of metal-oxide-Si (MOS) structures and characterised by measurements of their capacitance and ac-conductance as a function of gate-voltage. The frequency dependence of ac-electrical properties of Mn-oxide films and their variation with the annealing temperatures or crystal-structural content were studied. The measured values of the relative permittivity for Mn oxides of different crystal structures were tabulated. It was found that the obtained MnO oxide because of the annealing in vacuum at about 500 °C has the highest relative permittivity, about 10, which suggests it to be a candidate for high-k insulator on Si applications. It was found that the data of the ac-measurements follow the correlated barrier-hopping (CBH) model and the model's parameters were determined.     

Correlation between structural and electrical properties of ZnO thin films

Thin ZnO films were deposited by radio frequency (r.f.) and direct current (d.c.) magnetron sputtering techniques onto glass substrates. Microstructural and electrical properties of ZnO films were studied using X-ray diffractometer (XRD), scanning electron microscope (SEM) and resistivity measurements. It was found that the size of the crystallites in the d.c. deposited films increased with increasing film thickness, while the crystallite size of r.f. deposited films remained unchanged. The d.c. deposited grains also had much stronger orientation related to the substrate than the r.f. films. XRD data indicated that the thin films with d<350 nm for r.f. and <750 nm for d.c. films have a very high degree of ZnO nonstoichiometry. This agreed well with the conductivity measurements and R(T) behaviour of the films with different resistance R. It was also found that the electrical resistivity of the samples increased exponentially with the thickness of films.     

LPCVD生长结构层多晶硅和掺P多晶硅的工艺

对LPCVD生长结构层多晶硅和掺P多晶硅的原理进行了阐述,分析了薄膜质量与各项工艺参数的关系.实验时,对各项工艺参数进行调节,在保证薄膜质量和片内一致性的同时取得最大的生长速率.生长出来的多晶硅结构层厚度达到2μm;掺P多晶硅的厚度达到1OOOhA.     

Influence of nitrogen gas flow rate on the structural, morphological and electrical properties of sputtered TiN films

In this work, nanocrystalline titanium nitride (TiN) films have been deposited by reactive DC magnetron sputtering technique on the Si/SiO₂ (100) substrates. The influence of nitrogen gas flow rate [0, 3, 5, 7 and 9 sccm (standard cubic centimeter per minute)] on the structural, morphological and electrical properties of the nanocrystalline TiN films has been studied. As-deposited TiN films have been characterized by using X-ray diffraction (XRD), XPS (X-ray photoelectron spectroscopy), FESEM (field emission scanning electron microscopy) and four point probe resistivity measurement, respectively. The XRD patterns revealed the HCP symmetry for pure Ti (N₂ = 0 sccm) with (002) preferred orientations, and the FCC symmetry for TiN (N₂ = 3, 5, 7 and 9 sccm) films having (111) preferred orientations. The lattice parameters were found to be a = 2.950 ?, c = 4.681? for the Ti (N₂ = 0 sccm) film and a = 4.250Å for the TiN films. The presence of different phases such as TiN and TiO₂ were confirmed by XPS analysis. The FESEM images showed a smooth morphology of the film with columnar grain structures. The grain size of the TiN films was found to decrease from 22 to 15 nm as the nitrogen flow rate is increased from 0 to 9 sccm. The electrical resistivity measurement showed that the resistivity of the film increased from 11 × 10^?6 to 17 × 10^?6 Ohm cm on increasing nitrogen flow rate from 3 to 9 sccm, having the lowest resistivity of 11 × 10^?6 Ohm cm for the film deposited at 3 sccm nitrogen flow.     

The crystalline properties of nitrogen doped hydrogenated microcrystalline silicon thin films

The crystalline properties of nitrogen doped hydrogenated microcrystalline silicon thin films deposited by plasma enhanced chemical vapor deposition were studied. Gas phase doping density in the order of 10⁻² and 10⁻¹ leads to changes in the crystalline properties of the films. Raman scattering signals indicate that nitrogen doping causes a more significant reduction in crystallite size than does an increase in SiH₄ concentration. In addition, the size reduction occurs with a less significant increase in amorphous fraction volume than in the case of SiH₄ concentration increase. The N in the Si crystalline induces disorder or stress as a result of the higher electronegativity and smaller atomic size of N compared to Si. Thus, the crystallite size reduction is thought to occur to reduce the disorder in crystalline grain induced by doped nitrogen.     

The structural and electrical properties of Metglas and amorphous metal films

We prepared non-alloyed, alloyed and gas-doped metal films by vapour quenching under ultrahigh vacuum conditions in order to find non-crystalline phases. Of the metals investigated (titanium, zirconium, vanadium, niobium, chromium, molybdenum, nickel, platinum, cobalt, copper, tungsten and tantalum such as TaNi, TaCo, WN, TaAr and TaN exhibited a non-crystalline phase which we call metglas because of its structural similarity to bulk Metglas®. TaNi and TaN films exhibited in addition a non-crystalline structure which we call solid-amorphous. The criteria for the characterization of the metglas and solid-amorphous structure are given.     

Substrate temperature dependence of electrical and structural properties of Ru films

Microstructures and resistivities of sputtered Ru films were investigated as a function of substrate temperature to obtain a single-layered Ru barrier without a Ta/TaN under layer. High resistivity Ru films with a high density of crevices, which enhances Cu diffusion along the crevices, were formed by the conventional sputtering process, i.e., sputtering at room temperature and annealing at 400 °C-700 °C for 30 min in Ar + 3%H₂. But, crevice-free and smooth Ru films with low resistivity, the same as that for the bulk phase, were formed when substrate temperature add sputtering was raised to 700 °C. Ru films formed by this process had (002) preferred orientation and then Cu (111) was formed by plating. This result corresponded to the tendency predicted by ab initio calculations.     

The study of structural and electrical properties of thin antimony films

Structural and electrical properties of thin antimony films of various thicknesses evaporated on to glass substrates have been studied in the temperature range 150 to 350 K. The structural studies show that the films are polycrystalline having grains whose size increases with thickness. The electrical resistivity is found to increase as thickness decreases, thus exhibiting the size effect. The effect of grain-boundary scattering has been studied using a Mayadas-Shatzkes model and a three-dimensional model. The experimental results on the electrical resistivity are found to be consistent with the three-dimensional model. The specularity parameterp 0.49, and has no temperature dependence. The values of reflection coefficient,R, and transmission coefficient,t, are determined from the experimental data.     

Optical, structural and electrical properties of pure and urea doped KDP crystals

Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed.     

Effects of post-rapid thermal annealing on structural, electrical and optical properties of hydrogenated aluminum doped zinc oxide thin films

In this study, hydrogenated aluminum doped zinc oxide (HAZO) thin films were prepared by DC magnetron sputtering in different H₂/(Ar+H₂) volume ratio atmosphere. The effects of post-rapid thermal annealing (RTA) in Ar+8 % H₂ atmosphere on the structural, optical, and electrical properties of the thin films were investigated systematically. Results showed that the RTA treatment effectively improved the electrical conductivity of the HAZO thin films with small hydrogen content, due to the increase of the Hall mobility and the carrier concentration. The lowest resistivity of the HAZO thin film deposited in 8 % H₂ ratio atmosphere reached 6.3 × 10^?4 Ω cm after RTA. The improved electrical properties of the RTA-treated HAZO films were ascribed to the activation of Al dopants, the increase of oxygen vacancies and the desorption of negative charged oxygen species at the grain. These results implied that RTA process might be useful to fabricate high quality HAZO films with a low thermal budget.