Physical properties of thermally evaporated silicon films nitrided at different rf plasma-processing time

Nitrided surfaces and composition gradients in thin films exhibit interesting mechanical, electrical, and optical properties. Therefore, amorphous hydrogen-free silicon (a-Si) thin films were deposited by electron beam evaporation and subsequently nitrided by an inductively coupled rf plasma. The effects of successive plasma-processing cyclic time on structural and optical properties as well as electrical resistivity were examined by different characterization techniques. It was found that the rf plasma treatment has a massive effect on the physical properties of the Si films. The Si thin films were transformed gradually into nitrides compound and the amount of nitrogen in the film increased with increasing the rf plasma-processing time. The Si nitrided films showed structural, optical, and electrical properties dependent on the plasma-nitriding time. Increasing the rf plasma-processing time reduced the thickness, increased transmittance, increased resistivity, and decreased the reflectance of the nitrided Si films. The electrical resistivity increased to about nine orders of magnitude when the film was nitrided at a plasma-processing time of 25 min. The optical band gap increased from 2.42 to 3.52 eV with increasing the plasma-processing time from 10 to 35 min. The decrease in the refractive index with the increase in the plasma-processing time is attributed to the possible change in the bucking density as well as to the increase in the band gap.     

超声场作用下导电聚苯胺的合成

采用正相微乳液聚合法在超声波作用下制备导电聚苯胺,研究超声场强度的变化和作用时间的长短对导电聚苯胺的粒度和导电性能的影响。结果表明:与非超声场相比,采用超声场作用下正相微乳液聚合法制备的导电聚苯胺粉体的粒度显著降低,平均粒径从16.59μm减小到10.35μm。随着超声时间的增加,聚苯胺的电导率从5.230×10-2S/cm提高到1.923×10-1S/cm,提高了一个数量级。在超声波的作用下,聚苯胺粉体中分子间的偶极矩变化加强,超声作用产生的空化效应强化了十二烷基苯磺酸的掺杂和乳化作用。     

Enhanced conductivity in iodine doped polyaniline thin film formed by thermal evaporation

Thermal evaporation technique was employed to deposit pristine and iodine doped polyaniline (PANI) thin films on glass substrates. PANI was synthesized by the chemical oxidation method. Iodine doping was carried out by evaporation. The polymer synthesized was characterized by Thermo Gravimetric Analysis (TGA), Fourier Transform Infra Red (FTIR) and Ultraviolet-Visible (UV-VIS) spectroscopy. The evaporation temperature was optimized from TGA measurements. The thin film was deposited in vacuum at 1.33 × 10^− 4 Pa by thermal evaporation of PANI. The polymer film was characterized by FTIR and UV-VIS spectroscopy. The surface morphology of the films was studied by field emission scanning electron microscopy. The resistivity was measured by van der Pauw technique. The conductivity of the doped films was seen to increase with the iodine concentration and many fold increase in conductivity was observed in comparison to the pristine films. The increase in conductivity is due to the generation of polaron band in the band gap upon iodine doping.     

苯胺的等离子体聚合薄膜特性研究

采用苯胺的等离子体聚合法，得到致密高、化学稳定性好的自支撑膜。ＩＲ光谱和导电性研究表明，它与化学法聚合得到的聚苯胺有明显不同的结构和特性，而且研究结果提示用此方法可得到中红外区的红外吸收材料。鉴于等离子体聚合产物大多是非结晶的无定形结构，我们通过ＳＥＭ和ＨＥＥＤ研究发现，该聚合产物单晶存在，这对等离子体聚合的理论和实验研究有着积极的意义。．     

Electrical and optical properties of rf-sputtered CdTe films

In this paper some electrical and optical properties ofn-type CdTe films prepared by rf sputtering at 180 W power have been reported. For doping the films a number of pellets of pure Cd placed on the CdTe target were simultaneously sputtered with the target material to get Cd-doped CdTe films. The films after doping were foundn-type. Maximum doping concentration obtained this way was of the order of 10¹⁴ cm⁻³. XRF spectra of target material and the rf-sputtered films were found to be more or less similar. All the films were found to have large number of defects indicated by profound aging effect in the initial stages of aging. The films became stable for measurements after about 8–10 days. Activation energy and band gap found from the temperature dependence of dark conductivity were 0–5 eV and 1.43 eV respectively. Photoconductivity of the films was studied and the photoconductive rise time, decay time and the decay constants were determined from the photoconductive rise and decay curves at 500 Lx and 1000 Lx of intensity of illumination.     

Doping of rf plasma deposited diamond-like carbon films

Rf plasma deposited diamond-like carbon (DLC) films have been doped n-type with the addition of nitrogen as a feed gas to a magnetically confined rf plasma. Controlled amounts of nitrogen are added to the CH₄/He plasma and the films are characterised. The electronic properties together with the microstructure of the deposited films are examined. Activation energy studies show the Fermi level can be moved from 0.5 eV away from the valence band for the undoped DLC films, through a maximum activation energy of 0.9 eV corresponding to the midgap and to 0.45 eV away from the conduction band with maximum N incorporation. The optical band gap first increases, indicative of a reduction in the band-edge tail states, and then tends to a steady value of ˜2 eV. Activation energy studies together with the optical band gap data are used to analyse the density of states for the deposited films. The preferential doping configuration of the atomic nitrogen and the importance of the π-π* states for electronic conduction for DLC:N films is discussed in the light of the findings.     

Comparative study of chemically synthesized and plasma polymerized pyrrole and thiophene thin films

Pyrrole and thiophene polymers prepared via chemical means or plasma polymerization at different radio frequency (RF) power input on different substrates were compared using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and UV-visible absorption spectroscopy. These polymers were deposited as thin films on either low-density polyethylene (LDPE) or LDPE surface graft copolymerized with acrylic acid (AAc). The results indicate that the structures of plasma polymerized pyrrole and thiophene are rather different from those of polymers synthesized by conventional chemical methods, due to a higher degree of crosslinking and branching reactions in plasma polymerization. A higher and more stable conductivity can be obtained with chemically synthesized polypyrrole and polythiophene, but the thin films generated from the plasma polymerization process are much smoother and more uniform. The lack of stability in the plasma polymerized samples’ conductivity may be due to the unstable nature of the charge transfer complex with the dopant (iodine) resulting in a greater ease of diffusion of the iodine from the film. Under the conditions tested, the thickness of plasma polymerized pyrrole and thiophene thin layers increases almost linearly with the RF power. The modification of the LDPE substrates using AAc-graft copolymerization can enhance the growth and adhesion of the thin film and its conductivity.     

Investigation of structural,optical, antibacterial,and dielectric properties of V-doped copper oxide thin films: Comparison with undoped copper oxide thin films

Vanadium doped Copper oxide (CO) thin films were prepared by the sol-gel dip-coating method. The properties of thin films were examined by X-Ray Diffractometer (XRD), UV–Visible-NIR spectrophotometry, and dielectric properties analyzer. The antibacterial and photocatalytic properties were also determined. XRD spectra revealed the dual-phase of copper oxide (cuprite and tenorite) for all percentages of V with no other impurity peak. Tauc's relation is used to probe the optical band gap which is reduced from 1.96 to 1.64 eV with an increase in vanadium doping percentage. The impurity band coalesces with the conduction band of copper oxide to decrease the band gap. Dielectric constant measurements reveal that the Ac conductivity of thin films increases with an increase in V doping percentage.     

乳液聚合条件对聚苯胺性能的影响

以（NH4）2S2O8为催化剂,在非极性溶剂-功能质子酸-水三相体系中,采用乳液聚合方法合成聚苯胺。对乳液聚合与化学氧化溶液聚合合成的聚苯胺性能进行了比较,研究了掺杂酸、氧化剂、反应时间、温度等聚合条件对聚苯胺导电性、溶解性等性能的影响。结果表明,乳液聚合产率高于80%,聚苯胺电导率大于1S/cm,在有机溶剂中的溶解性与用化学氧化合成的聚苯胺比较有明显提高。     

The effects of the aluminium concentration on optical and electrical properties of AZO thin films as a transparent conductive layer

In this paper, we studied the effects of the aluminium dopant concentration on the optical and electrical properties of aluminium doped zinc oxide (AZO) thin films grown on soda-glass substrates by a simple chemical method. The amount of aluminium in the compound was varied from 0 to 5 atomic percent (at.%), and the typical thickness of the films produced was about 300 nm. The thin films were characterized by scanning electron microscopy and X-ray diffraction to investigate the morphology and crystallinity of the samples. The optical properties of the thin films were studied by UV–Vis spectroscopy to determinate absorption, transmittance, and the diffuse reflectance. In addition, the photoluminescence properties of the thin films, excited with a 320 nm UV laser beam, were investigated. The effects of the aluminium concentration on these optical properties are discussed. The films with 2 and 5 % doping had excellent optical transmittance (~85–90 %) in the 400–1100 nm wavelength range. The photoluminescence spectra of the AZO films revealed UV near band edge emission peaks in the 378–401 nm range and an oxygen-vacancy related peak around 471 nm. The addition of aluminium changed the band gap of zinc oxide from 3.29 to 3.41 eV, and the appearance of a new level was observed in the band gap at the higher aluminium doping concentrations. The AZO thin films showed good conductivity (in the order of 10^?2 Ω cm) which allows their use as transparent electrodes. Moreover, the AZO thin films were stable in open air for 30 days.     

Influence of iodine on the electrical properties of nickel phthalocyanines thin film devices

The electrical properties of pure Nickel Phthalocyanine (Ni Pc) thin films and iodine doped Ni Pc thin films with Gold and Aluminium electrode sandwiched devices have been investigated. The electrical properties and the various electrical parameters of the pure and iodine-doped films have been estimated and compared from the analysis of the current density characteristics. From our study we find that the iodine doping enhanced the electrical conductivity compared to pure Nickel Phthalocyanine and the conduction mechanism is much improved with the iodine doping. Interestingly these films after iodine doping showed remarkably increased electrical conductivity nearly ten times that of pure Phthalocyanine. This may be accounted for by the decrease in the metal-metal bond distance. At low voltages the film shows an ohmic conduction whereas at higher voltage levels the conduction is dominated by space charged limited conduction. Further the reverse conduction mechanisms have also been investigated for this sandwiched device. From the current limitations in the reverse condition a strong rectifying behaviour is evident.     

TiO_2光阳极表面原位聚合聚苯胺的制备及表征

为有效解决染料敏化太阳能电池(DSSC)的固态电解质与光阳极界面接触差的问题,文中采用化学原位聚合法在染料敏化TiO2光阳极表面制备聚苯胺(PANI)导电膜,研究了PANI成膜的最佳工艺参数。通过微观形貌观察及电导率测试说明,低温条件用樟脑磺酸(CSA)掺杂PANI薄膜颗粒细小均匀,电导率高达6.297S/cm。红外光谱分析表明,用CSA掺杂PANI较盐酸掺杂的电荷离域更充分,掺杂效果更好。PANI/Dye-TiO2复合膜在可见光区的吸收峰增多,吸收频带增宽;最后通过DSSC电池性能测试得到以PANI为电解质的DSSC较液态DSSC开路电压高,短路电流低的结果。     

Film-thickness effects on the optical and electrical properties of Cu-GeO2 thin cermet films

The effect of film thickness on the optical and electrical properties of Cu-30 wt % GeO₂-70 wt % thin cermet films prepared by electron-beam deposition at about 10^–3 Pa and at a substrate temperature of 300 K is reported. The ultraviolet, visible and direct current (d.c.) conductivity results are analysed with the aim of determining the optical band gap,E _opt, the width of the band tails,E _e, and the d.c. thermal activation energy,E _a. It was found that the optical energy gap increases with increasing thickness and that the absorption was due to indirect transitions ink-space. The general feature of the absorption edge remains similar for both unannealed and annealed films, but annealing has the effect of decreasingE _opt. The d.c. conductivity results show thatE _a decreases with increasing thickness. From a knowledge ofE _opt andE _a, a probable model of the electronic band structure in Cu-GeO₂ thin films has been suggested.     

A Study of the Structural, Optical and Electrical Properties of SnS Thin Films Modified by Plasma

SnS thin films were deposited by chemical bath deposition technique and treated using glow discharge 02 plasma. The pressure discharge was 3 Torr, discharge voltage of 2.5 kV and 20 mA of discharge current. The as-deposited and treated thin films were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The photoconductivity and electrical effects of SnS have been studied. The SnS thin films had an orthorhombic crystalline structure. The optical gap changed from 1.61 to 1.84 eV due to the 02 plasma treatment. The conductivity shows a marked increase with the treatment, from 2.56×10^-6 （Ω·cm）-1 for as-deposited film until 0.10 （Ω·cm）-1 for the film treated at 180 rain. This result is a suitable range of conductivity for the improvement of the solar cell with SnS as an absorber material.     

Structural,optical and electrical properties of CdZnS thin films

The thin films of Cd_1-x Zn _x S (x?=?0, 0.2, 0.4, 0.6, 0.8 and 1) have been prepared by the vacuum evaporation method using a mechanically alloyed mixture of CdS and ZnS. The structural, optical and electrical properties have been investigated through the X-ray diffractometer, spectrophotometer and Keithley electrometer. The X-ray diffraction patterns of these films show that films are polycrystalline in nature having preferential orientation along the (002) plane. In the absorption spectra of these films, absorption edge shifts towards lower wavelength with the increase of Zn concentration. The energy band gap has been determined using these spectra. It is found that the energy band gap increases with increasing Zn concentration. The electrical conductivity of so prepared thin films has been determined using a I–V characteristic curve for these films. The result indicates that the electrical conductivity decreases with increasing Zn content and increases with temperature. An effort has also been made to obtain activation energy of these films which increases with increasing Zn concentration in CdS.     

Influence of incorporation of Al3+ ions on the structural, optical and AC impedance characteristics of spin coated ZnO thin films

Aluminium doped zinc oxide thin films were deposited onto glass substrate using spin coating technique. The effects of Al doping on structural, optical and electrical properties of these films were investigated. X-ray diffraction analysis showed that all the thin films were of polycrystalline hexagonal wurtzite structure with (002) as preferential orientation except 2 at.% of Al doped ZnO films. The optical band gap was found to be 3.25 eV for pure ZnO film. It increases up to 1.5 at.% of Al doping (3.47 eV) and then decreased slightly for the doping level of 2 at.% (3.42 eV). The reason for this widening of the optical band gap up to 1.5 at.% is well described by Burstein–Moss effect. The photoluminescence spectra of the films showed that the blue shift and red shift of violet emission were due to the change in the radiative centre between zinc vacancy and zinc interstitial. Variation in ZnO grain boundary resistance against the doping concentration was observed through AC impedance study.     

低温等离子体聚合物薄膜的研究及应用

概述了利用低温等离子体技术制备有机聚合物薄膜、主要合成方法、特性及研究现状 ,简要讨论了等离子体聚合条件对薄膜结构和性质的影响 ,介绍了现代分析技术对聚合物薄膜结构的表征 ,阐述了近年来对低温等离子体聚合物薄膜的物理性质 ,包括表面性质、渗透性、电学和光学性质等方面的研究进展 ,并描述了其在工业生产各方面的一些应用     

Synthesis,transport and dielectric properties of polyaniline/Co<Subscript>3</Subscript>O<Subscript>4</Subscript> composites

Conducting polyaniline/cobaltous oxide composites have been synthesized using in situ deposition technique by placing fine graded/cobaltous oxide in polymerization mixture of aniline. The a.c. conductivity and dielectric properties are studied by sandwiching the pellets of these composites between the silver electrodes. It is observed that the values of conductivities increase up to 30 wt% of cobaltous oxide in polyaniline and decrease thereafter. Initial increment in conductivity is due to extended chain length of polyaniline where polarons possess sufficient energy to hop between favourable sites. Beyond 30 wt% of cobaltous oxide in polyaniline, blocking of charge carriers takes place reducing the conductivity values. It can be noted that the value of dielectric constant increases up to 10 wt% of cobaltous oxide. Thereafter, it decreases up to 30 wt% of cobaltous oxide and again increases up to 40 wt% of cobaltous oxide and decreases thereafter. The observed behaviour is attributed to the variation of a.c. conductivity. And it is observed that the dielectric loss increases up to 10 wt% of cobaltous oxide in polyaniline, decreases to a lower value of 20 wt% of cobaltous oxide and increases to 35 wt% and thereafter decreases. These values go in accordance with the values of dielectric constant. The results obtained for these composites are of greater scientific and technological importance.     

N-doped Zn15Sb85 phase-change materials for higher thermal stability and lower power consumption

Comparing to un-doped Zn₁₅Sb₈₅ material, N-doped Zn₁₅Sb₈₅ material had higher crystallization temperature, lower conductivity and better data retention. The optical band gap was derived from the transmittance spectra and a significant increase was observed with increasing nitrogen doping concentration. The measurement of atomic force microscopy indicated that the crystallization was inhibited and the surface of thin films became smoother after N doping. Phase change memory devices based on N-doped Zn₁₅Sb₈₅ thin film were fabricated to test and verify their electrical properties.     

Electrical and optical properties of phthalocyanine films

Thin films of various phthalocyanines (Pcs) were sublimed onto quartz glass in ultrahigh vacuum. The electrical and optical properties were studied without breaking the ultrahigh vacuum. The dyes were purified by repeated sublimation in vacuum.The conductivity varied with pretreatment (modification) and temperature. Exposure to oxygen, iodine and bromine increased the p-type conductivity by orders of magnitude and lithium doping caused n-type conductivity. Heavy exposure to halogens caused not only broadening of the optical absorption band but also bleaching. Annealing in vacuum removed the electrical and optical effects of doping nearly completely.Field effect studies were used to identify p- and n-type conductivity, to determine the drift mobility and to estimate the trap densities. The field effect and the photoconductivity of p- and n-type films increased by several orders of magnitude with the dark conductivity, i.e. with doping. This correlation is attributed either to traps with a continuous distribution in energy or to trapping by at least two discrete defect levels crossing the Fermi level within the surface-induced accumulation layer. Possible consequences for the sensitivity of semiconductor gas sensors are discussed.