Optical and structural characteristics of ZnO thin films grown by rf magnetron sputtering

Nanostructured ZnO thin films on Pyrex glass substrates were deposited by rf magnetron sputtering at different substrate temperatures. Structural features and surface morphology were studied by X-ray diffraction and atomic force microscopy analyses. Films were found to be transparent in the visible range above 400 nm, having transparency above 90%. Sharp ultraviolet absorption edges around 370 nm were used to extract the optical band gap for samples of different particle sizes. Optical band gap energy for the films varied from 3.24 to 3.32 eV and the electronic transition was of the direct in nature. A correlation of the band gap of nanocrystalline ZnO films with particle size and strain was discussed. Photoluminescence emission in UV range, which is due to near band edge emission is more intense in comparison with the green band emission (due to defect state) was observed in all samples, indicating a good optical quality of the deposited films.     

Effects of sputtering pressure and Al buffer layer thickness on properties of AZO films grown by rf magnetron sputtering

Transparent and conductive Al-doped (2 wt.%) zinc oxide (AZO) films were deposited on inexpensive soda-lime glass substrates by using rf magnetron sputtering at room temperature. This study analyzed the effects of argon sputtering pressure, which varied in the range from 0.46 to 2.0 Pa, on the morphological, electrical and optical properties of AZO films. The only (0 0 2) diffraction peak of the film were observed at 2θ～34.45°, exhibiting that the AZO films had hexagonal ZnO wurtzite structure, and a preferred orientation with the c-axis perpendicular to the substrate. By applying a very thin aluminum buffer layer with the thickness of 2 nm, findings show that the electrical resistivity was 9.46 × 10⁻⁴ Ω-cm, and the average optical transmittance in the visible part of the spectra was approximately 81%. Furthermore, as for 10 nm thick buffer layer, the electrical resistivity was lower, but the transmittance was decreased.     

Electrical and optical properties of ZnO:Al thin films grown by magnetron sputtering

The properties of transparent conductive ZnO:Al thin films grown by R.F. magnetron sputtering method are investigated. The working pressure (argon gas) is changed from 2.5 to 40.0 mTorr to study its influence on the characteristics of ZnO:Al thin films. The ZnO:Al thin films have better texture due to the increase in the surface mobility, which resulted from the increase in the mean free path of sputtering gas under lower working pressure. The microstructure of ZnO:Al films is found to be affected obviously by changing the working pressure. It is shown that the grain size of ZnO:Al thin films decreases with the increase of working pressure. The X-ray diffraction patterns indicate that the poor crystallized structure of ZnO:Al films is obtained at higher working pressure. Except 40 mTorr, the highly (002)-oriented ZnO:Al thin films can be found at the measured range of working pressure. Moreover, the growth rate of the films decreases from 1.5 to 0.5 nm/min as the working pressure increases from 2.5 to 40.0 mTorr. The results of optical transmittance measurement of ZnO:Al thin films reveal a high transmittance (>80%) in visible region and exhibit a sharp absorption edge at wavelength about 350 nm.     

Annealing effects on structural and optical properties of ZnMgO films grown by RF magnetron sputtering

Two sets of ZnMgO thin films have been fabricated on Si (111) substrates by RF magnetron sputtering, and were annealed at air atmosphere afterwards. The effects of annealing temperature and time on structural and optical properties were also characterized by X-ray diffraction, scanning electron microscopy and photoluminescence (PL) spectra. For samples fabricated at a lower temperature (200 °C, defined as samples I), the experimental results revealed that only hexagonal phase was observed for the films annealed at the temperature range from 180 to 420 °C, and the best crystal quality for the films was found at 240 °C. For samples synthesized at 220 °C (defined as samples II), the crystal structures exhibited anneal-time dependent. The experimental results revealed coexistence of hexagonal and cubic phase when they were annealed at a set temperature of 220 °C with the different annealing time, and the best one can be observed when the anneal time was 30 min. PL spectra showed blue shift for UV peak with the increase of annealing temperature for samples I, and the UV emission occurred red shift and then blue shift when the anneal time increased from 20 to 30 min for samples II.     

Ellipsometry study of InN thin films prepared by magnetron sputtering

Indium nitride (InN) thin films have been deposited on Si(1 0 0) substrates at temperature of 100–400 °C by reactive radio frequency (RF) magnetron sputtering. We measured the ellipsometric spectra of the InN film samples, and obtained the optical constants for the wavelength range of 410–1100 nm. The absorption edge of the InN films is 1.85–1.90 eV. The thicknesses of various InN films are found to be dependent on the substrate temperature.     

Study of the structural and optical properties of GaPN thin films grown by magnetron RF sputtering

GaP_1−xN_x thin films were deposited on glass substrates by RF sputtering employing a nitrogen-argon atmosphere in a partial pressure of 2×10⁻² Torr. We varied the growth temperature in the range 420-520 °C. The film's optical properties were studied by transmittance and absorbance spectroscopy. Characterization by scanning electron microscopy in cross-sectional view, atomic force microscopy, and X-ray diffraction was performed to determinate the film thickness, surface morphology, and crystal structure, respectively. Raman spectroscopy was employed to analyze the structural properties of samples. The GaP_1−xN_x films presented a cubic polycrystalline structure with a preferential orientation along the [1 1 1] direction. By varying the growth conditions we were able to change the band gap energy between 1.35 and 1.98 eV.     

Preparation and optical properties of Bi doped ZnO thin films with (100) orientation by rf magnetron sputtering

Bi doped ZnO films with (100) orientation have been grown on glass substrates by rf magnetron sputtering followed by vacuum annealing at 400 °C for 3 h. X-ray diffraction (XRD) revealed that the film first growth along (002) direction was suppressed to form (100) plane with c-axis parallel to the substrate. After annealed at 400 °C for 3 h under vacuum, transmittance about 80% in visible region and near 100% absorption in UV region for (100) oriented Bi doped ZnO films are confirmed by the optical transmission spectra. The optical band gap is evaluated to be around 3.13 eV which is lower than (002) oriented films.     

Effects of heat treatment on properties of ITO films prepared by rf magnetron sputtering

Indium tin oxide (ITO) films were deposited on glass substrates by rf magnetron sputtering using a ceramic target (In₂O₃-SnO₂, 90-10 wt%) without extra heating. The post annealing was done in air and in vacuum, respectively. The effects of annealing on the structure, surface morphology, optical and electrical properties of the ITO films were studied. The results show that the increase of the annealing temperature improves the crystallinity of the films, increases the surface roughness, and improves the optical and electrical properties. The transmittance of the films in visible region is increased over 90% after the annealing process in air or in vacuum. The resistivity of the films deposited is about 8.125×10⁻⁴ Ω cm and falls down to 2.34×10⁻⁴ Ω cm as the annealing temperature is increased to 500°C in vacuum. Compared with the results of the ITO films annealed in air, the properties of the films annealed in vacuum is better.     

Structure and magnetic properties of Fe epitaxial thin films prepared by UHV rf magnetron sputtering on GaAs single-crystal substrates

Fe thin films were prepared on GaAs single-crystal substrates of (100)_B3, (110)_B3, and (111)_B3 orientations by ultra high vacuum rf magnetron sputtering. The effects of substrate orientation and substrate temperature on the film growth, the structure, and the magnetic properties were investigated. On GaAs(100)_B3 substrates, Fe(100)_bcc single-crystal films are obtained at 300 °C, whereas Fe films consisting of bcc(100) and bcc(221) crystals epitaxially grow at room temperature (RT). Fe(110)_bcc and Fe(111)_bcc single-crystal films are respectively obtained on GaAs(110)_B3 and GaAs(111)_B3 substrates at RT-300 °C. The in-plane lattice spacings of these Fe epitaxial films are 0-9% larger than the out-of-plane lattice spacings due to accommodation of lattice mismatch between the films and the substrates. The film strain is decreased by employing an elevated substrate temperature of 300 °C. The in-plane magnetization properties are reflecting the magnetocrystalline anisotropy of bulk bcc-Fe crystal.     

Effect of substrate temperature on the structure and optical properties of ZnO thin films deposited by reactive rf magnetron sputtering

Zinc Oxide films were deposited on quartz substrates by reactive rf magnetron sputtering of zinc target. The effect of substrate temperature on the crystallinity and band edge luminescence has been studied. The films deposited at 300 °C exhibited the strongest c-axis orientation. AFM and Raman studies indicated that the films deposited at 600 °C possess better overall crystallinity with reduction of optically active defects, leading to strong and narrow PL emission.     

Fabrication of cerium oxide films on sapphire by rf magnetron sputtering

Results are presented of experiments to fabricate preferentially (200) oriented CeO₂ films without mechanical stresses on Al₂O₃ substrates. Pis’ma Zh. Tekh. Fiz. 25, 47–51 (June 12, 1999)     

Characterization of organic polymer thin films deposited by rf magnetron sputtering

Organic polymer thin films deposited by sputtering using polytetrafluoroethylene (PTFE) and polyimide (PI) targets were investigated with Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). Films deposited from the PTFE target were poly-hydro-fluoro-carbon. The thin films showed water repellency with an H₂O contact angle of about 110° and were transparent in the visible region. C-F combination states in the films were similar to those of bulk PTFE. Films deposited from the PI target were found to contain C-N bonds and were harder than bulk PI. The color of thin films was dark brown, showing the existence of C-N bonds, such as those in imide and/or amide groups. However, the combination states characterized by FTIR and XPS analyses were considerably different from those of bulk PI. The difference in chemical composition and combination states between the films deposited from PTFE and PI is thought to result from the difference in types of particles sputtered from the targets; in the case of PTFE sputtering, less C-F bonds are broken by collision of Ar ions for sputtering, whereas in the case of PI sputtering, C-H and C-C bonds are broken by collision of Ar ions.     

Structural and electrical properties of cerium dioxide films grown by RF magnetron sputtering

A systematic study was performed on the structural and electrical properties of cerium dioxide thin films grown on Si substrate with various deposition temperatures by RF magnetron sputtering. The films grown at 200°C are partly amorphous whereas those grown above 250°C are polycrystalline. An amorphous layer of SiO₂ forms at the interface between the cerium dioxide film and the Si substrate. Cerium dioxide film grown at higher temperatures up to 500°C sustains more leakage current on the basis of current-voltage measurements. The electrical conduction of the films is well fitted by a power-law relation, which is explained as space-charge-limited current conduction with exponential distributed traps in the band gap. The variations of dielectric constant, flatband voltage, fixed oxide charge and interface-trapped charge with deposition temperature were studied by making capacitance-voltage measurements on an Al/CeO₂/Si structure. The variations of electrical properties with temperature are strongly correlated with the formation of an amorphous SiO₂ layer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural and optical properties of La-doped ZnO films prepared by magnetron sputtering

La-doped ZnO films were prepared by RF magnetron sputtering using different composition powder compacted targets (0, 1, 2, 3 and 5 at.%). All films show a preferred c-axis growth orientation. Furthermore, the (002) diffraction peak shifts to a small angle and the full-width at half-maximum augments with increasing La concentration up to 2 at.%, which indicate that a small quantity of La atoms are incorporated into the ZnO lattice. The average transmittance in the visible range is over 80%, and a blue shift of the absorption edge is observed. With increasing La concentration, the band gap of ZnO films evaluated by the linear fitting linearly increases from 3.270 to 3.326 eV. In the photoluminescence spectra, a strong violet emission peak and a weak green emission band can be observed. The former is due to the electron transition between the defect energy levels, associated with the interfacial traps existing at the ZnO grain boundaries, and valence band. The latter could be ascribed to crystal defects related to oxygen vacancies.     

Electrical, optical, and structural properties of InZnSnO electrode films grown by unbalanced radio frequency magnetron sputtering

We have investigated the electrical, optical, structural, and annealing properties of indium zinc tin oxide (IZTO) films prepared by an unbalanced radio frequency (RF) magnetron sputtering at room temperature, in a pure Ar ambient environment. It was found that the electrical and optical properties of unbalanced RF sputter grown IZTO films at room temperature were influenced by RF power and working pressure. At optimized growth condition, we could obtain the IZTO film with the low resistivity of 3.77 × 10^− 4 Ω cm, high transparency of ~ 87% and figure of merit value of 21.2 × 10^− 3Ω^− 1, without the post annealing process, even though it was completely an amorphous structure due to low substrate temperature. In addition, the field emission scanning electron microscope analysis results showed that all IZTO films are amorphous structures with very smooth surfaces regardless of the RF power and working pressure. However, the rapid thermal annealing process above the temperature of 400 °C lead to an abrupt increase in resistivity and sheet resistance due to the transition of film structure from amorphous to crystalline, which was confirmed by X-ray diffraction examination.     

Electrical and optical properties of NiO composite films by radio frequency magnetron sputtering

The 100-nm NiO-Ag composite films with Ag content of 0 to 24.4 at.% are deposited on glass substrates. It is found that an ultra high electric resistivity (rho) value is obtained and cannot be detected by four point probe measurement when the Ag content is less than 3.4 at.%. The rho value is reduced significantly to 29.0 Omega-cm as Ag content is increased to 4.2 at.%, and it decreases greatly to 0.009 Omega-cm as the content of Ag is further increased to 24.4 at.%. The NiO-Ag composite film with Ag content of 4.2 at.% shows p-type conduction. However, it becomes n-type when the Ag content increases to 9.3 at.%, which results from the Ag atoms segregated at grain boundary of NiO when the excess Ag atoms are added into NiO films. On the other hand, the transmittance of the NiO-Ag films drops continuously from 96.3% to 31.6% as the Ag content increases from 0 to 24.4%.     

射频磁控溅射制备Mn掺杂ZnO薄膜的结构与光学性能

采用反应射频磁控溅射方法制备Zn1-xMnxO薄膜(0≤x≤0.25),并在不同温度下进行退火处理.通过原子力显微镜、薄膜X射线衍射、透射电子显微镜和透射光谱对薄膜的成分、表面形貌、微结构和光学性质进行了研究.结果表明,薄膜结晶质量明显地依赖于掺杂Mn元素的浓度,所有薄膜都表现了沿(002)晶面方向择优取向生长,当Mn...     

磁控溅射制备TbFeCo薄膜及其光学和磁光性质研究

采用放电等离子烧结(SPS)TbFeCo合金靶,分别在Si衬底和K9玻璃衬底上磁控溅射制备了磁光薄膜TbFeCo/Si和TbFeCo/K9;利用扫描型可变入射角全自动椭偏仪,室温下测量了复介电常数谱,测量结果表明两样品介电函数值有较大差异,说明衬底对薄膜的光学性质有重要影响.用磁光Kerr谱仪,在室温下分别测量了TbFeCo薄膜的极向Kerr回线和横向Kerr回线,发现所制备TbFeCo薄膜不具有垂直磁化性质,而呈现出面内磁化性质.     

Thin films prepared by sputtering MgF2 in an rf planar magnetron

Magnesium fluoride granules have been sputtered in an rf planar magnetron at 20 MHz. Films deposited in Ar developed a strong optical absorption at high power levels arising from fluorine depletion and magnesium oxidation. The latter was attributed to a reaction between residual water vapour and the dissociated compound. Films prepared at a low power input with a growth rate of about 2 nm min^?1 had the lowest optical absorption and a refractive index near to that of bulk MgF₂ but their growth was too slow for most practical uses. The magnetron discharge probably resulted in greater target dissociation than a non-magnetron discharge operated at the same power input because of the ion impact localisation at the magnetron target. Film analysis showed that biasing the film substrate positively with respect to ground to enhance impact of fluorine negative ions raised the fluorine content of the film. Sputtering in a CF₄+Ar+O₂ mixture to enhance fluorine sorption by the film and reduce carbon deposition by oxidation was ineffective. The resultant deposit was a fluorocarbon polymer with a low Mg/F content.     

Thickness dependence of structure and optical properties of silver films deposited by magnetron sputtering

A series of silver films with different thickness were prepared under identical conditions by direct current magnetron sputtering. The optical properties of the silver films were measured using spectrophotometric techniques and the optical constants were calculated from reflection and transmission measurements made at near normal incidence. The results show that the optical properties and constants are affected by films' thickness. Below the critical thickness of 17 nm at which Ag film forms a continuous film, the optical properties and constants vary significantly as the thickness of films increases and then tends to a stable value which is reached at 41 nm. X-ray diffraction measurements were carried out to examine the structure and stress evolution of the Ag films as a function of films' thickness. It was found that the interplanar distance of (111) orientation decreases when the film thickness increases and tends to be close to that of bulk material. The compressive strains also decrease with increasing thickness.