The influence of deposition rate on the stress and microstructure of AlN films deposited from a filtered cathodic vacuum arc

Aluminium nitride (AlN) thin films have been reactively deposited using a filtered cathodic vacuum arc system. A pulsed substrate bias was applied in order to increase the average energy of the depositing species. The stress and microstructure of the films were determined as a function of the deposition rate and pulse bias amplitude/frequency. The stress generated in films grown with high voltage pulsed bias depended on the deposition rate and a transition from tensile stress to compressive stress occurred as the deposition rate increased. This trend was accompanied by progressive changes in the microstructure. In order of increasing deposition rate, the films exhibited: a porous structure with tensile stress; a dense AlN film with compressive stress; and a dense AlN film showing evidence of a thermally induced reduction in stress.     

Effect of lattice-mismatch strain on the structural and dielectric properties of (Pb,Sr)TiO3 thin films grown by pulsed laser deposition

Pb_0.35Sr_0.65TiO₃ (PST) thin films have been fabricated on LaAlO₃ (LAO) and MgO substrates using the pulsed laser deposition technique. The microstructure characteristics of the films were examined by means of X-ray diffraction, atomic force microscopy, scanning electron microscopy and Raman spectroscopy, and the results indicate that the films are epitaxially grown and show good crystallinity. The dielectric constant dependence on DC bias voltage and temperature were measured in a planar capacitor configuration for these films. Compared to the PST thin film grown on LAO, the film grown on MgO showed a higher temperature of the capacitance maximum and a higher dielectric constant at zero bias. We explain the results by taking into account the lattice-mismatch strain between the substrate and the film. In contrast to the in-plane compressive strain induced by the LAO substrate, the in-plane tensile strain induced by the MgO substrate enlarges the unit cell of PST and enhances the magnitude of dipole moments, which increases the dielectric constant. These results indicate that a reasonable in-plane tensile strain could improve the dielectric properties of PST thin films.     

Influence of substrate bias voltage on properties of Pt thin films deposited by non-mass separated ion beam deposition method

Pt thin films were deposited on Si substrates by applying a negative substrate bias voltage using a non-mass separated ion beam deposition method. The effect of the substrate bias voltage on the properties of the deposited films was investigated. In the case of Pt thin films deposited without the substrate bias voltage, a columnar structure and small grains were observed. The electrical resistivity of the deposited Pt films was very high (49.3 ± 0.65 µΩ cm). By increasing the substrate bias voltage, no clear columnar structure was observed. At the substrate bias voltage of − 75 V, the resistivity of the Pt film showed a minimum value of 16.9 ± 0.2 µΩ cm closed to the value of bulk (10.6 µΩ cm).     

Influence of substrate temperature and bias voltage on the optical transmittance of TiN films

Titanium nitride (TiN) thin films were prepared by means of reactive DC sputtering on quartz and sapphire substrates. Structural, electrical and optical effects of deposition parameters such as thickness, substrate temperature, substrate bias voltage were studied. The effect of substrate temperature variations in the 100-300°C range and substrate bias voltage variations in the 0-200 V DC range for 45-180 nm thick TiN films were investigated. Temperature-dependent electrical resistivity in the 100-350 K range and optical transmission in the 300-1500 nm range were measured for the samples. In addition, structural and morphological properties were studied by means of XRD and STM techniques.The smoothest surface and the lowest electrical resistivity was recorded for the optimal samples that were biased at about V_s=−120 V DC. Unbiased films exhibited a narrow optical transmission window between 300 and 600 nm. However, the transmission became much greater with increasing bias voltage for the same substrate temperature. Furthermore, it was found that lower substrate temperatures produced optically more transparent films.Application of single layers of MgF₂ antireflecting coating on optimally prepared TiN films helped increase the optical transmission in the visible region to more than 40% for 45 nm thick samples.     

Growth of diborides thin films on different substrates by pulsed laser ablation

The growth of scandium, titanium and zirconium diborides thin films by pulsed laser ablation technique on different substrates has been studied. In situ reflection high energy electron diffraction and ex situ X-ray diffraction analyses indicate that the films are strongly c-axis oriented on all the substrates and also epitaxial, apart from Si(111), where the in plane orientation is poor. Atomic force microscopy imaging reveals a flat surface in all the epitaxial samples, with roughness lower than 1 nm. The results on silicon carbide and sapphire are very promising for using these materials as buffer layers in magnesium diboride thin films growth, especially to improve epitaxy and to prevent oxygen diffusion from the substrate, and also to study the influence of lattice strain on MgB₂ critical temperature.     

Investigation of Pb-Mg-Nb-O pyrochlore thin films for tunable material

PMN thin films have been investigated as a feasible material for tunable microwave applications. PMN thin films were deposited by RF magnetron sputtering from Pb₆MgNb₆O₂₂ ceramic target on platinized Si substrates. The crystallinity, thickness, surface morphology, dielectric property, and voltage tunable properties of thin films were investigated by means of X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and an impedance analyzer. The influences of sputtering substrate temperature and post-annealing on the tunable dielectric properties of thin films were investigated. Increasing the sputtering substrate temperature and annealing temperature can significantly increase tunability; however, these relations had the limitation that overly annealing temperature degraded the tunability of the thin film. A tunability of 38% at 1100 kV/cm of dc bias field under 1 MHz was achieved for a sample sputtered at 550 °C and annealed at 700 °C.     

Electrical transport mechanism in plasma polymerized 2, 6, diethylaniline thin films

Plasma polymerized 2, 6, diethylaniline (PPDEA) thin films were deposited at room temperature on to glass substrates by a capacitively coupled parallel plate glow discharge reactor. The surface of the PPDEA thin films has been found uniform and pinhole free from the scanning electron micrographs. The observation by electron dispersive X-ray analysis indicates the presence of carbon, nitrogen and oxygen in the PPDEA thin films. The current density-voltage characteristics of aluminum (Al)/PPDEA/Al structure of different film thicknesses have been studied at different temperatures. In the low voltage region, the conduction current obeys Ohm's law while the charge transport phenomenon appears to be Schottky type in the higher voltage region. The temperature dependence of the current density for different bias voltages was also investigated which confirms the possibility of Schottky emission in PPDEA thin films as well.     

FeNi and Ti underlayers for vertical recording on rigid disks

FeNi and Ti underlayers on CoCr disks are studied. It is confirmed that the structure of FeNi thin films is derived from pure Ni cfc structure. Soft magnetic films can be achieved when sputtering conditions are optimized for an Fe2ONi80 target. Sputtering conditions were also studied for Ti layers. It was found that Ti thin films crystallize in the hcp structure. An (002) crystallographic preferred orientation was generally observed, but it can be improved for thinner films and when high cathode voltage is used during deposition. A (100) orientation is observed if high bias voltage is applied to the substrate during deposition. Both structures, when used as underlayers, improve the vertical anisotropy of CoCr, but (100) Ti underlayers lead to a higher vertical anisotropy     

反应溅射TiN纳米晶薄膜的结构特征和耐蚀性

利用直流反应溅射技术在不锈钢和硅基体上沉积了TiN纳米晶薄膜,采用场发射扫描电镜(FESEM)、X射线衍射(XRD)和电化学阻抗谱(EIS)技术研究了薄膜的表面形貌、相结构和耐蚀性与偏压的关系。结果表明,TiN薄膜的表面结构明显取决于所施加的偏压,适当提高偏压有利于获得细小、均匀、致密和光滑的膜层。XRD分析发现,TiN薄膜为面心立方结构,其择优取向为(111)面。实验显示,对应0V和-35V偏压的薄膜为欠化学计量比的,而偏压增加至-70V和-105V时的薄膜为化学计量比的TiN。EIS结果表明,较高偏压下的TiN薄膜几乎在整个频率范围内均表现为容抗特征,其阻抗模值明显高于低偏压下的膜层,这主要与较高偏压下的薄膜具有相对致密的微结构有关。较低偏压的TiN薄膜因结构缺陷较多其耐蚀性低于基体不锈钢。EIS所揭示的薄膜结构特征与FESEM观测结果一致。可见,减少穿膜针孔等结构缺陷有利于改善反应溅射TiN纳米晶薄膜耐蚀性。     

Charge-carrier injection into pentacene thin film formed on Si(111) probed by STM spectroscopy

The injection of charge carriers into a pentacene thin film formed on a Si substrate was investigated by scanning tunneling microscopy (STM). Tip height versus bias voltage (z-V) spectroscopy reveals the characteristic charge transport properties of the molecular film, i.e., the conductivity and the threshold energy of charge injection. The abrupt descent of the tip into the film owing to the transition of film conductance, which depends on the degree of charge carrier injection, was observed for crystallized pentacene thin films. The lower film conductance at around zero bias voltage is still higher than that of a vacuum. This indicates that the carrier injection barrier between the pentacene and the semiconducting substrate is extremely low. The convergence of the carrier injection endpoints into a narrow range of electric-field intensity implies that the main factor contributing to barrier formation and collapse is not the bias voltage but the electric field.     

Dependence of the electrical and optical properties on the bias voltage for ZnO:Al films deposited by r.f. magnetron sputtering

Aluminum-doped zinc oxide (ZnO:Al) thin films were deposited on glass, polycarbonate (PC), and polyethylene terephthalate (PET) substrates by r.f. magnetron sputtering. The substrate dc bias voltage varied from 0 V to 50 V. Structural, electrical and optical properties of the films were investigated. The deposition rate of ZnO:Al films on glass substrate initially increased with the bias voltage, and then decreased with further increasing bias voltage. It was found that the best films on glass substrate with a low as 6.2 × 10^− 4 Ω cm and an average transmittance over 80% at the wavelength range of 500-900 nm can be obtained by applying the bias voltage of 30 V. The properties of the films deposited on polymer substrate, such as PC and PET, have a similar tendency, with slightly inferior values to those on glass substrate.     

Influence of sputtering parameters on crystalline structure of ZnO thin films

The relations between the sputtering parameters and the crystalline microstructure of ZnO thin films are presented. The energetic bombardment of substrate by neutral atoms, ions and electrons during sputtering is characterized by total energy flux density which affects the film. This parameter can be estimated by RF power, substrate bias voltage and concentration of reactive gases. Substrate temperature and total energy flux density are the major parameters which have a significant influence on ZnO thin film crystalline structure.     

钼薄膜的制备、力学性能和磨损性能

采用直流磁控溅射技术在GCr15轴承钢底材上沉积了钼薄膜。利用XRD，AFM对不同负偏压下沉积的钼薄膜的结构和表面形貌进行了表征；利用纳米压痕仪对薄膜的硬度和膜基结合强度进行了测定；最后利用DF-PM型动静摩擦系数精密测定仪和扫描电镜(SEM)研究了薄膜的硬度、残余模量与负偏压的关系。结果表明：利用直流磁控溅射法制备的钼薄膜的硬度随负偏压的变化存在最大值，另外负偏压还影响薄膜的微结构、粗糙度以及膜基结合力，但负偏压的改变对钼薄膜的摩擦系数影响不大。     

纳米结构TiN薄膜的制备及其摩擦学性能

在室温条件下,用磁过滤等离子体装置在单晶硅基底上制备了纳米结构TiN薄膜分析了薄膜的表面形貌、晶体结构,测量了TiN薄膜的硬度,研究了基底偏压对薄膜结构性能的影响.结果表明,用此方法制备的TiN薄膜表面平整光滑,颗粒尺寸为50～80 nm;随着基底偏压的增大薄膜发生(111)面的择优取向随着偏压的提高,薄膜的颗粒度稍有增大,摩擦系数增大,偏压提高,晶面在较密排的(111)面有强烈的择优取向,硬度也有所增大.在其它条件相同的情况下载荷越大,摩擦系数越大.不起用磁过滤等离子体法制备的纳米结构TiN薄膜具有较低的摩擦系数(0.14～0.25).     

Nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition

Nano-polycrystalline vanadium oxide thin films have been successfully produced by pulsed laser deposition on Si(100) substrates using a pure vanadium target in an oxygen atmosphere. The vanadium oxide thin film is amorphous when deposited at relatively low substrate temperature (500 degrees C) and enhancing substrate temperature (600-800 degrees C) appears to be efficient in crystallizing VOx thin films. Nano-polycrystalline V3O7 thin film has been achieved when deposited at oxygen pressure of 8 Pa and substrate temperature of 600 degrees C. Nano-polycrystalline VO2 thin films with a preferred (011) orientation have been obtained when deposited at oxygen pressure of 0.8 Pa and substrate temperatures of 600-800 degrees C. The vanadium oxide thin films deposited at high oxygen pressure (8 Pa) reveal a mix-valence of V5+ and V4+, while the VOx thin films deposited at low oxygen pressure (0.8 Pa) display a valence of V4+. The nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition have smooth surface with high qualities of mean crystallite size ranging from 30 to 230 nm and Ra ranging from 1.5 to 22.2 nm. Relative low substrate temperature and oxygen pressure are benifit to aquire nano-polycrystalline VOx thin films with small grain size and low surface roughness.     

Investigation of titanium nitride films deposited at room temperature by energetic cluster impact

Energetic cluster impact (ECI) deposition was applied to grow titanium nitride films on silicon (100) substrate at room temperature. Proton elastic scattering (PES), X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to characterize the composition, structure and morphology of TiN_x films, respectively. The PES results reveal that the films are N-deficient and there exists a certain amount of oxygen impurity in the films. It is found from the XRD results that the structure of TiN_x films is sensitive to experimental conditions such as nitrogen gas partial pressure, sputtering current and substrate bias voltage and that TiN_x films are (220) preferred orientation within some range of experimental conditions. The AFM observation indicates that the films become more uniform and compact with increasing substrate bias voltage. The root mean square roughness also decreases with increasing bias voltage. Some interpretation for the above results are also given in this paper.     

CNx薄膜的结构、力学性能和摩擦学性能

采用射频磁控溅射方法制备了非晶CNx薄膜。利用纳米硬度计研究了薄膜沉积过程中基体负偏压对薄膜硬度和弹性的影响。利用X光电子能谱分析了CNx薄膜的结构。另外 ,还研究了在微动摩擦实验中振动频率、振幅和载荷对摩擦系数的影响。     

Synthesis and optical characterization of amorphous carbon nitride thin films by hot filament assisted RF plasma CVD

Carbon nitride thin films were synthesized by hot filament assisted radio frequency plasma chemical vapour deposition using methane and nitrogen gas mixture on silicon and glass substrates. The films were deposited at different substrate bias and at different substrate temperatures. At higher substrate bias (>−120 V) there was no deposition on the substrate, but complete etching of the deposited layer was observed. X-ray diffraction studies indicated the films were amorphous. The Fourier transform infrared spectra showed that the films produced exhibited high transmittance with the presence of the C-N stretching band at 1260 cm⁻¹. For the films deposited at a lower substrate temperature C=N peaks were also present. Raman spectroscopic study indicated the presence of D and G peaks whose relative height varied with substrate temperature. The transmittance versus wavelength measurement in the UV-VIS-NIR region showed the high transmittance in the NIR region. The optical band gap of the films was calculated to be 2.0 eV and the refractive index varied within 1.6-1.7 for the wavelength range 800-1800 nm.     

Effect of bias voltage on microstructure and mechanical properties of nanocrystalline TiN films deposited by reactive magnetron sputtering

Nanocrystalline TiN films deposited under various bias voltages have been prepared by a reactive magnetron sputtering. The effect of bias voltage on the microstructural morphologies of the TiN films was characterized by FE-SEM and AFM. The texture of the TiN films was characterized by XRD. It is also observed that the crystallite size decreases with increasing bias voltages. However, rms roughness increases with increasing bias voltages. The changes in roughness and crystallite size in the TiN thin films are due to one or a combination of factors such as resputtering, ion bombardment, surface diffusivity and adatom mobility; the influence of each factor depends on the processing conditions.     

The properties of samarium doped ceria oxide thin films grown by e-beam deposition technique

One of the main challenges in today's solid oxide fuel cell (SOFC) technology is the reduction of their operating temperature. New types of oxygen ion conducting materials are currently under investigation to overcome the problems which SOFC faces at high temperatures. Samarium doped ceria oxide (SDC) was the material of investigation in this work. Optical quartz (SiO₂) and Fe–Ni–Cr alloy (Alloy 600) were the two types of chosen substrates onto which SDC thin films were deposited by e-beam evaporation technique. The bias voltage was applied to the substrate during film growth. It had an influence on film formation, its microstructure and density because of the ionized particles presence in the SDC vapor stream. Changes in crystallite size and surface morphology were determined from X-ray diffraction data and scanning electron microscopy images. Influence of bias voltage on porosity of formed SDC thin films on optical quartz were calculated from transmittance spectra data by using Swanepoel method. The porosity decreases up to 12% by decreasing bias voltage from 0 to ?150 V.