Effect of RF power on the optical and morphological properties of RF plasma polymerised linalyl acetate thin films

Thin films derived from linalyl acetate were fabricated using the Radio Frequency (RF) plasma polymerisation technique between RF power levels of 10 and 75 W. The optical properties of the films were investigated using spectroscopic ellipsometry and UV-vis spectroscopy between 200 and 1000 nm. An optical band gap of approximately 3 eV for all power levels was determined from Tauc plots. The surface morphology and hardness of the material were studied using AFM and nano-indentation respectively to determine the effect of RF power on the thin film properties. Smooth surfaces with an average roughness of approximately 0.2 nm with consistent morphology were obtained across all power levels, while hardness demonstrated a linearly increasing dependence on RF deposition power, with values ranging between 0.29 and 0.44 GPa. These studies indicate the ability to tailor film characteristics by varying the RF deposition power, and the potential for the films to be used within electronic devices as encapsulation layers, insulating layers, or as semiconducting layers with the introduction of charge carriers to the chemical structure of the material.     

RF sputtered thin films of highT cY-Ba-Cu-O

Y-Ba-Cu-O films are grown on strontium titanate substrates by RF sputtering from a single composite target. A barium-deficient annular ring with diameter equal to that of the target dimension is repeatedly observed. Films inside this ring are deposited exclusively at the close target-substrate distance. At larger distances the films grow more in exterior regions rather than in the interior region of the ring. Stoichiometry, structural morphology and superconducting transition temperatures are studied for various regions of the film. The films are superconducting when sintered in flowing oxygen at 950°C with onset at 100 K and a broad transition width.     

Preparation and infrared emissivity of ZnO: Al (AZO) thin films

ZnO:Al(AZO) thin films with different Al-doped concentration were developed under different temperature. The effects of the temperature and Al-doped concentration on the infrared emissivity were investigated. Results show that the crystalline phase of the AZO films is hexagonal wurtzite which is the same as that of the un-doped ZnO film. The crystalline size become larger and the particle shapes become more regular with the increase of temperature, which lead to the increase of resistivity and the decreases of the infrared emissivity.     

Seebeck and magnetoresistive effects of Ga-doped ZnO thin films prepared by RF magnetron sputtering

In this paper, Ga-doped ZnO (GZO) films were deposited on glass substrates at different substrate temperatures by RF magnetron sputtering. The effect of substrate temperature on the structural, surface morphological properties, Seebeck and magnetoresistive effects of GZO films was investigated. It is found that the GZO films are polycrystalline and preferentially in the [0 0 2] orientation, and the film deposited at 300 °C has an optimal crystal quality. Seebeck and magnetoresistive effects are apparently observed in GZO films. The thermoelectromotive forces are negative. Decreasing substrate temperature and annealing in N₂ flow can decrease carrier concentration. The absolute value of the Seebeck coefficient increases with decreasing carrier concentration. The maximal absolute value of Seebeck coefficient is 101.54 μV/K for the annealed samples deposited at the substrate temperature of 200 °C. The transverse magnetoresistance of GZO films is related to both the magnetic field intensity and the Hall mobility. The magnetoresistance increases almost linearly with magnetic field intensity, and the films deposited at higher substrate temperature have a stronger magnetoresistance under the same magnetic field, due to the larger Hall mobility.     

Fabrication of p-ZnO:ZrN thin films by RF magnetron sputtering

An attempt has been made to fabricate p-ZnO thin films from the ZrN mixed ZnO targets by RF magnetron sputtering. The targets of different ZrN concentrations (0, 1, 2, and 4?mol%) have been prepared by solid-state reaction route. The ZrN-codoped ZnO films grown on semi-insulating Si (100) substrates have been characterized by X-ray diffraction (XRD), photoluminescence (PL), Hall effect measurement, time-of-flight secondary ion mass spectrometer (ToF-SIMS), and atomic force microscopy (AFM). XRD studies reveal that all films are oriented along (002) plane. The Hall measurements showed p-conductivity for 1 and 2?mol% ZrN-codoped ZnO films. Further, it has been found that 1?mol% ZrN-codoped film has low resistivity (7.5?×?10^?2?Ω?cm) and considerable hole concentration (8.2?×?10¹⁸?cm^?3) by optimum incorporation of nitrogen due to best codoping. The red shift in near-band-edge emission observed from PL well acknowledged the p-conduction in 1 and 2?mol% ZrN-codoped ZnO film. The incorporation of N and Zr atoms in the ZnO matrix has been confirmed by ToF-SIMS analysis. The increase in peak to valley roughness (R _pv) with increase of doping concentration has been observed from AFM analysis. ZnO homojunction has also been fabricated with the best codoped p-ZnO film and it showed typical rectification behavior of a diode. The junction parameters have also been determined for the fabricated homojunction.     

射频功率对类金刚石薄膜性能的影响

在不同射频功率条件下,实验研究了射频等离子体化学气相沉积类金刚石薄膜的金刚石相分数、光学常数和硬度。利用Raman光谱仪、椭圆偏振仪、数字式显微硬度计分别测试了不同条件下单层类金刚石薄膜的金刚石相分数、光学常数和硬度。实验表明,随着功率的增加,金刚石相的相对分数减少,薄膜的折射率先减小再增加然后减小,射频功率大于910 W时,沉积速率急剧增大。而薄膜的硬度先增加后减小,在射频功率为860 W处获得最大值。     

射频功率对类金刚石薄膜性能的影响

在不同射频功率条件下,实验研究了射频等离子体化学气相沉积类金刚石薄膜的金刚石相分数、光学常数和硬度。利用Raman光谱仪、椭圆偏振仪、数字式显微硬度计分别测试了不同条件下单层类金刚石薄膜的金刚石相分数、光学常数和硬度。实验表明,随着功率的增加,金刚石相的相对分数减少,薄膜的折射率先减小再增加然后减小,射频功率大于910 W时,沉积速率急剧增大。而薄膜的硬度先增加后减小,在射频功率为860 W处获得最大值。     

Effect of RF power and sputtering pressure on the structural and optical properties of TiO2 thin films prepared by RF magnetron sputtering

TiO₂ thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples deposited at various RF powers and sputtering pressures and post annealed at 873 K, were characterized using X-ray diffraction (XRD), micro Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectrum indicates that the films are amorphous-like in nature. But micro-Raman analysis shows the presence of anatase phase in all the samples. At low sputtering pressure, increase in RF power favors the formation of rutile phase. Presence of oxygen defects, which can contribute to PL emission is evident in the XPS studies. Surface morphology is much affected by changes in sputtering pressure which is evident in the SEM images. A decrease in optical band gap from 3.65 to 3.58 eV is observed with increase in RF power whereas increase in sputtering pressure results in an increase in optical band gap from 3.58 to 3.75 eV. The blue shift of absorption edge in all the samples compared to that of solid anatase is attributed to quantum size effect. The very low value of extinction coefficient in the range 0.0544-0.1049 indicates the excellent optical quality of the samples. PL spectra of the films showed emissions in the UV and visible regions.     

High-performance UV detector based on Ga-doped zinc oxide thin films

High-quality ultraviolet photoconductive detectors have been fabricated using Ga-doped zinc oxide layers grown by spray pyrolysis on glass substrates. The performance of the photoconductivity has been tested by the measurements of the current-voltage (I-V) characteristics under forward and reverse bias. The devices have been characterized to investigate the effect of buffer layer on the detector performances. The behaviour of photocurrent with respect to optical power density, wavelength and chopping time has been investigated. We achieved the highest responsivity of about 1125 A/W at 5 V bias at 365 nm peak wavelength. Our approach provides a simple and cost-effective way to fabricate high-performance ‘visible-blind’ UV detectors.     

Characteristics of ZnO:In thin films prepared by RF magnetron sputtering

In-doped ZnO (ZnO:In) transparent conductive thin films were deposited on glass substrates by RF magnetron sputtering. The effect of substrate temperature on the structural, electrical and optical properties of the ZnO:In thin films was investigated. It was found that higher temperature improves the crystallinity of the films and promotes In substitution easily. ZnO:In thin films with the best crystal quality were fabricated at 300 °C, which exhibit a larger grain size of 29 nm and small tensile strain of 0.9%. The transmittance of all the films was revealed to be over 85% in the visible range independence of the substrate temperatures and the lowest resistivity of ZnO:In thin films is 2.4×10⁻³ Ω cm.     

Characteristics of ZnO:In thin films prepared by RF magnetron sputtering

In-doped ZnO (ZnO:In) transparent conductive thin films were deposited on glass substrates by RF magnetron sputtering. The effect of substrate temperature on the structural, electrical and optical properties of the ZnO:In thin films was investigated. It was found that higher temperature improves the crystallinity of the films and promotes In substitution easily. ZnO:In thin films with the best crystal quality were fabricated at 300 °C, which exhibit a larger grain size of 29 nm and small tensile strain of 0.9%. The transmittance of all the films was revealed to be over 85% in the visible range independence of the substrate temperatures and the lowest resistivity of ZnO:In thin films is 2.4×10⁻³ Ω cm.     

UV laser-induced grating formation in PDMS thin films

Excimer laser (193 nm and 157 nm) induced ablation and structure formation in poly-dimethylsiloxane (PDMS) thin films is demonstrated. Ellipsometric measurements provide values of the optical constants of the films as well as their thicknesses, which are below 1 m. At fluences above 160 mJ/cm² two pulses of UV light induce gratings with at minimum 1-m periods and crossed gratings with 4-m periods. The structure heights are between 10 nm and 20 nm with ridge widths of several hundred nanometres. The ablation occurs after a single incubation pulse with a threshold that increases logarithmically with the ablation wavelength increasing from 157 nm to 1064 nm. At 193 nm the ablation rate for 2 J/cm² is 127 nm/pulse. PACS 79.20.La; 34.50.Dy; 68.55.Jk     

The effects of substrate temperatures on the electrical properties of CaZrO3 thin films prepared by RF magnetron sputtering

The radio frequency magnetron sputtering technology (RFMS) was employed to deposit perovskite structure orthogonal phase CaZrO₃ thin films on Pt/Ti/SiO₂/Si substrates. The effects of substrate temperatures on structure and electrical properties of these films were investigated in detail. The CaZrO₃ thin films were systematically characterized by means of X-ray diffraction (XRD), Scanning electron microscope (SEM), Multi-frequency LCR meter (HP4294A) and Radiant Precision Workstation to study the phase structure, cross-section morphology, dielectric and ferroelectric properties at different substrate temperatures. The result indicates that these films can withstand 80 V DC Bias voltage and have excellent stability of frequency, voltage and temperature. The CaZrO₃ thin film prepared at 550 °C turned out to be mainly orthorhombic CaZrO₃ phase with high permittivity, low dielectric loss, extremely low leakage current (at 1 MHz, the dielectric constant is 39.42, the dielectric loss is 0.00455, the quality factor is 220 and the leakage current density is 9.11 × 10⁻⁷A/cm² at 80 V applied voltage.). This work demonstrates that higher substrate temperature can boost the formation of orthorhombic CaZrO₃ phase and the CaZrO₃ thin film prepared by RF magnetron sputtering is a very promising paraelectric material in the application of thin film capacitor.     

Highly sensitive ethanol sensors based on nanocrystalline SnO2 thin films

This paper reports on a simple and inexpensive ultrasonic spray pyrolysis method to synthesize agglomerate-free nanosized SnO₂ particles with a size smaller than 10 nm. Scanning electron microscopy, transmission electron microscopy and high resolution X-ray diffraction studies were used to characterize the morphology, crystallinity, and structure of the SnO₂ particles. Under the optimized experimental conditions, the prepared SnO₂ sensor shows the high response (S = 491) towards 100 ppm ethanol gas at 300 °C, linearity in the range of 100–500 ppm, quick response time (2 s), recovery time (60 s) and selectivity against other gases. The response of the sensor was monitored in a 250–450 °C temperature range. The seven fold enhancement in gas response and selective detection of C₂H₅OH in the presence of other gases such as CH₃OH and CH₃CHOHCH₃ are the significant points in this investigation. These results demonstrate that pure nanocrystalline SnO₂ thin film can be used as the sensing material for fabricating high performance ethanol sensors.     

BiFeO3 thin films: Novel effects

In this paper we report synthesis of phase-pure highly resistive magnetoelectric BiFeO₃ thin films on Pt/TiO₂/SiO₂/Si substrate by using pulsed laser deposition technique. For the first time saturated ferroelectric hysteresis loop has been observed. It has confirmed the presence of ferroelectricity in BiFeO₃ compound. The films exhibit dielectric anomaly near Neel temperature. This anomaly is related to the influence of vanishing magnetic order on the electric order. In situ domain alignment occurs during observation of the films under transmission electron microscope.     

Doped thin metal oxide films for catalytic gas sensors

TiO₂ and Pt doped TiO₂ thin films were grown by pulsed laser deposition on 〈0 0 1〉 SiO₂ substrates. The doped films were compared with undoped ones deposited in similar experimental conditions. An UV KrF* (λ = 248 nm, τ_FWHM ≅ 20 ns, ν = 2 Hz) excimer laser was used for the irradiation of the TiO₂ or Pt doped TiO₂ targets. The substrate temperatures were fixed during the growth of the thin films at values within the 300-500 °C range. The films’ surface morphology was investigated by atomic force microscopy and their crystalline quality by X-ray diffractometry. The corresponding transmission spectra were recorded with the aid of a double beam spectrophotometer in the spectral range of 400-1100 nm. No contaminants or Pt segregation were detected in the synthesized anatase phase TiO₂ thin films composition. Titania crystallites growth inhibition was observed with the increase of the dopant concentration. The average optical transmittance in the visible-infrared spectral range of the films is higher than 85%, which makes them suitable for sensor applications.     

Optical constants of DUV/UV fluoride thin films

High-refractive-index materials LaF3, NdF3, and GdF3 and low-refractive-index materials MgF2, A1F3, and Na3A1F6 single thin films are deposited by a resistive-heating boat at different depositing rates and specific substrate temperatures on single crystal MgF2 substrates. Transmittances of all fluoride thin films are measured using commercial spectrometer in the ambient atmosphere and under vacuum using synchrotron radiation instrument in the wavelength region from 190 to 500 am. The optical constants of these materials are determined by envelope method and iterative algorithm on the basis of transmittance measurements.     

射频溅射制备的BST薄膜介电击穿研究

采用射频溅射制备BST薄膜，研究了薄膜的介电击穿特性.实验表明，在电压增大到传统击穿电压(电流密度出现瞬时增大时的电压)之前，薄膜性能已被破坏，发现在传统击穿状态之前存在另一个新状态——初始击穿状态.通过测试各状态的J-V(电流密度-电压)、J-T(电流密度-温度)特性分析其导电机理，建立了薄膜结构、漏电性能随电场强度增大而变化的模型.最后提出了确定实际意义上击穿电压的方法. 关键词： BST薄膜 介电击穿 漏电流     

射频功率对类金刚石薄膜结构和性能的影响

利用直流-射频-等离子体增强化学气相沉积技术在单晶硅表面制备了类金刚石薄膜，采用原子力显微镜、Raman光谱、x射线光电子能谱、红外光谱和纳米压痕仪考察了射频功率对类金刚石薄膜表面形貌、微观结构、硬度和弹性模量的影响.结果表明，制备的薄膜具有典型的含H类金刚石结构特征，薄膜致密均匀，表面粗糙度很小.随着射频功率的升高，薄膜中成键H的含量逐渐降低，而薄膜的sp3³含量、硬度以及弹性模量先升高， 后降低，并在射频功率为100W时达到最大. 关键词： 等离子增强化学气相沉积 类金刚石薄膜 射频功率 结构和性