High-index low-loss gallium phosphide thin films fabricated by radio frequency magnetron sputtering

High-index low-loss Gallium Phosphide thin films for visible light have been produced by radio frequency magnetron sputtering in an argon environment. This broadens the high refractive index limit of transparent optical materials using a physical deposition process. Energy-dispersive x-ray analysis and spectroscopic ellipsometry were used to characterize the stoichiometry and optical properties. A post-deposition high-temperature anneal was found to be necessary to restore the proper stoichiometric ratio and to reduce the absorption. The annealing conditions were optimized by an in-situ fiber-optic transmission spectrum monitoring system. The films exhibit a high refractive index (N = 3.23) and a low extinction coefficient (K = 0.029) at 633 nm. Such high index GaP films have broad applications in nanophotonic device designs.     

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%.     

a-Si:H/SiO2 multilayer films fabricated by radio-frequency magnetron sputtering for optical filters

We examined the optical properties of a-Si:H/SiO2 multilayer films fabricated by radio-frequency magnetron sputtering for optical bandpass filters (BPFs). Because of the high refractive-index contrast between a-Si:H and SiO2, the total number of layers of an a-Si:H/SiO2 multilayer can be relatively small. We obtained an a-Si:H refractive index of 3.6 at lambda = 1550 nm and its extinction coefficient k < 1 x 10(-4) and confirmed by Fourier-transform infrared spectroscopy that such small k is influenced by the Si-H bonding in the film. We fabricated a-Si:H/SiO2 BPFs by using in situ optical monitoring. Thermal tuning of a-Si:H/SiO2 BPF upon a silica substrate was also performed, and a thermal tunability coefficient of 0.07 nm/degree C was obtained.     

Nanoporous Ti-metal film deposition using radio frequency magnetron sputtering technique for photovoltaic application

Nanoporous Ti-metal film electrode was fabricated by radio frequency (rf) magnetron sputtering technique on nanoporous TiO2 layer prepared by sol-gel combustion method and investigated with respect to its photo-anode properties of TCO-less DSCs. The porous Ti layer (approximately 1 microm) with low sheet resistance (approximately 17 Omega/sq.) can collect electrons from the TiO2 layer and allows the ionic diffusion of I(-)/I(3-) through the hole. The porous Ti layer with highly ordered columnar structure prepared by 8 mTorr sputtering shows the good impedance characteristics. The efficiency of prepared TCO-less DSCs sample is about 4.83% (ff: 0.6, Voc: 0.65 V, Jsc: 11.2 mA/cm2).     

Growth of thin Ag films produced by radio frequency magnetron sputtering

Thin Ag films in the thickness range D = 14–320 nm were deposited by radio frequency magnetron sputtering on glass substrates at room temperature inside a vacuum chamber with base pressure of about 5 × 10^− 6 Pa. The growth of the films was studied via X-ray diffraction and atomic force microscopy experiments. The two techniques are complementary and give us the opportunity to study the surface roughness, the statistical distribution and the average value of the grain size, as well as the texture of the samples. It is shown that the film roughness increases negligibly within the first 60 atomic layers of growth. The thicker films (D 300 nm) develop a nanocrystalline structure with a root mean square roughness of about 2.5 nm. The grain size evolves linearly with the thickness from 9.4 nm at D = 54 nm to 31.6 nm at D = 320 nm.     

溅射法生长 MgxZn1- xO薄膜的结构和光学特性

用射频磁控溅射法在不同衬底上制备出了MgxZn1-xO薄膜。X射线衍射(XRD)和原子力显微镜(AFM)研究结果表明,薄膜为六角纤锌矿结构,具有(002)方向择优取向;随氧分压增加,(002)衍射峰的角度变大,表征薄膜表面粗糙程度的方均根粗糙度减小。室温光致发光谱中有多个紫外及可见光致发光峰,其中344nm发光峰应来源于近带边发射。室温透射谱表明薄膜在可见光区具有极高的透过率,薄膜的吸收边位于340nm附近,进而估算出Mg、Zn1-xO薄膜的带隙宽度为3．59eV,与光致发光结果一致。     

Non-magnetic hexagonal nanocrystalline ni films grown by radio frequency magnetron sputtering

Nanoscale Ni films in the thickness range 15-500 nm were grown on various substrates, such as amorphous glass, single crystalline silicon and sapphire, and polycrystalline alumina, at a temperature of about 350 K by radio frequency magnetron sputtering. It is demonstrated, via X-ray diffraction and high-resolution transmission electron microscopy, that there is an Ar-gas pressure window that favors the growth of stable single-phase hexagonal nanocrystalline Ni films regardless of the film thickness and the kind of the substrate. At lower or higher Ar pressures the films grow in the regular face centered cubic phase of Ni. The structural habits are attributed to differences in the kinetic energy of the Ni atoms impinging on the substrates. Superconducting quantum interference device magnetometry measurements reveal that the hexagonal films show zero magnetic response down to liquid Helium temperature. This result is discussed with respect to earlier first principle calculations and to experimental results on Ni nanoparticles.     

Structural, electrical and optical properties of zirconium-doped zinc oxide films prepared by radio frequency magnetron sputtering

Transparent and conducting zirconium-doped zinc oxide films have been prepared by radio frequency magnetron sputtering at room temperature. The ZrO₂ content in the target is varied from 0 to 10 wt.%. The films are polycrystalline with a hexagonal structure and a preferred orientation along the c axis. As the ZrO₂ content increases, the crystallinity and conductivity of the film are initially improved and then both show deterioration. Zr atoms mainly substitute Zn atoms when the ZrO₂ content are 3 and 5 wt.%, but tend to cluster into grain boundaries at higher contents. The lowest resistivity achieved is 2.07 × 10^− 3 Ω cm with the ZrO₂ content of 5 wt.% with a Hall mobility of 16 cm² V^− 1 s^− 1 and a carrier concentration of 1.95 × 10²⁰ cm^− 3. All the films present a high transmittance of above 90% in the visible range. The optical band gap depends on the carrier concentration, and the value is larger at higher carrier concentration.     

Characterization of zirconium oxynitride films obtained by radio frequency magnetron reactive sputtering

Thin ZrN_xO_y films are deposited on Si (100) substrates by radio frequency (RF) reactive magnetron sputtering of a zirconium target in an argon-oxygen-nitrogen mixture. The Φ_N2/Φ_{(Ar + N2 + O2)} ratio was varied in the range 2.5%-100% while the oxygen flux was kept constant. The films were characterized by combining several techniques: X-ray photoelectron spectroscopy, X-ray diffraction and Secondary Ion Mass Spectroscopy. The relationship between structural and compositional properties and the sputtering parameters was investigated. Increasing nitrogen partial pressure in the gas mixture, a chemical and structural evolution happens. At lowest nitrogen flux, ZrN cubic phase is formed with a very small amount of amorphous zirconium oxynitride. At highest nitrogen flux, only crystalline ZrON phases were found. For the films obtained between these two extremes, a co-presence of ZrN and ZrON can be detected. In particular, chemical analysis revealed the co-presence of ZrO₂, ZrN, ZrON and N-rich zirconium nitride which is correlated with the Φ_N2/Φ_{(Ar + N2 + O2)} values. A zirconium nitride crystal structure with metal vacancies model has been considered in order to explain the different chemical environment detected by X-ray photoelectron spectroscopy measurements. The metal vacancies are a consequence of the deposition rate decreasing due to the target poisoning. It's evident that the growth process is strongly influenced by the zirconium atoms flux. This parameter can explain the structural evolution.     

Properties of TaSiN thin films deposited by reactive radio frequency magnetron sputtering

TaSiN is a promising material for application as electrically conductive diffusion barrier for the integration of high permittivity perovskite materials in integrated circuits. TaSiN thin films were deposited by reactive radio frequency magnetron sputtering using TaSi and TaSi_2.7 targets in an Ar/N₂ atmosphere. The sputter power was varied in order to achieve different TaSiN compositions. The stoichiometry of as-deposited films was estimated using Rutherford backscattering spectroscopy. The as-deposited TaSiN thin films are amorphous. Their crystallization temperature is above 700 °C and increases with higher nitrogen content. They have metallic conduction and ohmic behavior. The resistivity of as deposited films is in the range from 10^− 6 Ω m up to 10^− 3 Ω m and increases with nitrogen content. It was found that p⁺⁺-Si/Ta₂₁Si₅₇N₂₁ develops unacceptable high contact resistance. Introducing an intermediate Pt layer the stack p⁺⁺-Si/Pt/Ta₂₁Si₅₇N₂₁ had a good conductive properties and good thermal stability at 700 °C.     

Fluorine-doped ZnO transparent conducting thin films prepared by radio frequency magnetron sputtering

Fluorine-doped ZnO transparent conducting thin films were prepared by radio frequency magnetron sputtering at 150 °C on glass substrate. Thermal annealing in vacuum was used to improve the optical and electrical properties of the films. X-ray patterns indicated that (002) preferential growth was observed. The grain size of F-doped ZnO thin films calculated from the full-width at half-maximum of the (002) diffraction lines is in the range of 18-24 nm. The average transmittance in visible region is over 90% for all specimens. The specimen annealed at 400 °C has the lowest resistivity of 1.86 × 10^− 3 Ω cm, the highest mobility of 8.9 cm² V^− 1 s^− 1, the highest carrier concentration of 3.78 × 10²⁰ cm^− 3, and the highest energy band gap of 3.40 eV. The resistivity of F-doped ZnO thin films increases gradually to 4.58 × 10^− 3 Ω cm after annealed at 400 °C for 4 h. The variation of the resistivity is slight.     

Electrical and optical properties of indium tin oxide films prepared on plastic substrates by radio frequency magnetron sputtering

The influence of deposition power, thickness and oxygen gas flow rate on electrical and optical properties of indium tin oxide (ITO) films deposited on flexible, transparent substrates, such as polycarbonate (PC) and metallocene cyclo-olefin copolymers (mCOC), at room temperature was studied. The ITO films were prepared by radio frequency magnetron sputtering with the target made by sintering a mixture of 90 wt.% of indium oxide (In₂O₃) and 10 wt.% of tin oxide (SnO₂). The results show that (1) average transmission in the visible range (400-700 nm) was about 85%-90%, and (2) ITO films deposited on glass, PC and mCOC at 100 W without supplying additional oxygen gas had optimum resistivity of 6.35 × 10⁻⁴ Ω-cm, 5.86 × 10⁻⁴ Ω-cm and 6.72 × 10⁻⁴ Ω-cm, respectively. In terms of both electrical and optical properties of indium tin oxide films, the optimum thickness was observed to be 150-300 nm.     

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.     

Structural, optical and electrical properties of AZO/Cu/AZO tri-layer films prepared by radio frequency magnetron sputtering and ion-beam sputtering

Highly conducting tri-layer films consisting of a Cu layer sandwiched between Al-doped ZnO (AZO) layers (AZO/Cu/AZO) were prepared on glass substrates at room temperature by radio frequency (RF) magnetron sputtering of AZO and ion-beam sputtering of Cu. The tri-layer films have superior photoelectric properties compared with the bi-layer films (Cu/AZO, AZO/Cu) and single AZO films. The effect of AZO thickness on the properties of the tri-layer films was discussed. The X-ray diffraction spectra show that all films are polycrystalline consisting of a Cu layer with the cubic structure and two AZO layers with the ZnO hexagonal structure having a preferred orientation of (0 0 2) along the c-axis, and the crystallite size and the surface roughness increase simultaneously with the increase of AZO thickness. When the AZO thickness increases from 20 to 100 nm, the average transmittance increases initially and then decreases. When the fixed Cu thickness is 8 nm and the optimum AZO thickness of 40 nm was found, a resistivity of 7.92 × 10⁻⁵ Ω cm and an average transmittance of 84% in the wavelength range of visible spectrum of tri-layer films have been obtained. The merit figure (F_TC) for revaluing transparent electrodes can reach to 1.94 × 10⁻² Ω⁻¹.     

The optical emission spectroscopy study of an rf-plasma-enhanced magnetron sputtering system

Optical emission spectroscopy has been performed for unbalanced DC magnetron sputtering of Cu in Ar atmosphere with the enhanced ionization of inductively coupled plasma. The intensities of Cu, Cu⁺, Ar and Ar⁺ lines were measured at various discharge parameters such as pressure and rf power. Both Cu and Cu⁺ lines intensities initially increase and then decrease with increasing pressure. At the same time, Ar line intensity increases and the Ar⁺ line intensity decreases with increasing pressure. With increasing rf power, all the lines intensities increase at different rates and become saturated when the rf power is greater than 700 W. The rf discharge exhibits mode jumping (E-mode to H-mode) and hysteresis phenomena. When the rf power increases to 400 W, the rf discharge mode jumps from E-mode to H-mode. When the rf power input decreases from 800 to 300 W, the rf discharge mode jumps back from H-mode to E-mode. However, during the mode change, the intensities of all lines are higher when switching from H-mode to E-mode than those when switching from E-mode to H-mode at the same rf power. In the rf power region, the ionization of Cu is significantly enhanced. The reasons of these phenomena are discussed.     

Application of optical broadband monitoring to quasi-rugate filters by ion-beam sputtering

Methods for the manufacture of rugate filters by the ion-beam-sputtering process are presented. The first approach gives an example of a digitized version of a continuous-layer notch filter. This method allows the comparison of the basic theory of interference coatings containing thin layers with practical results. For the other methods, a movable zone target is employed to fabricate graded and gradual rugate filters. The examples demonstrate the potential of broadband optical monitoring in conjunction with the ion-beam-sputtering process. First-characterization results indicate that these types of filter may exhibit higher laser-induced damage-threshold values than those of classical filters.     

陶瓷靶射频磁控溅射TiO2薄膜的制备和光催化特性

Transparent titania thin films were prepared on glass substrates by radio frequency magnetron sputtering from TiO2 ceramic target. The structure and morphology of those films with different sputtering power and substrate temperature has been measured with X-ray diffractometer (XRD) and atomic force microscope (AFM). It was found that the films were anatase and a mix of anatase-rutile with different condition. The transmission of the films has been studied by using UV-VIS-NIR spectrometer. It shows absorption edge has a little red shift with the increase of sputtering power and substrate temperature. The photocatalytic activity of the films was tested on the degradation of Rhodamine B solution. T.he highest degradation efficiency in our experiment was obtained in the film deposited at 550℃ and 130W.     

Indium tin oxide films deposited on polyethylene naphthalate substrates by radio frequency magnetron sputtering

Indium tin oxide (ITO) thin films were deposited on unheated polyethylene naphthalate substrates by radio-frequency (rf) magnetron sputtering from an In₂O₃ (90 wt.%) containing SnO₂ (10 wt.%) target. We report the structural, electrical and optical properties of the ITO films as a function of rf power and deposition time. Low rf power values, in the range of 100-130 W, were employed in the deposition process to avoid damage to the plastic substrates by heating caused by the plasma. The films were analyzed by X-ray diffraction and optical transmission measurements. A Hall measurement system was used to measure the carrier concentration and electrical resistivity of the films by the Van der Pauw method. The X-ray diffraction measurements analysis showed that the ITO films are polycrystalline with the bixbite cubic crystalline phase. It is observed a change in the preferential crystalline orientation of the films from the (222) to the (400) crystalline orientation with increasing rf power or deposition time in the sputtering process. The optical transmission of the films was around 80% with electrical resistivity and sheet resistance down to 4.9 × 10^- 4 Ωcm and 14 Ω/sq, respectively.     

Structures and properties of the Al-doped ZnO thin films prepared by radio frequency magnetron sputtering

Al-doped ZnO thin films were deposited by radio frequency magnetron sputtering using a ZnO target with 2 wt.% Al₂O₃. The structures and properties of the films were characterized by the thin film X-ray diffraction, high resolution transmission electron microscopy, Hall system and ultraviolet/visible/near-infrared spectrophotometer. The Al-doped ZnO film with high crystalline quality and good properties was obtained at the sputtering power of 100 W, working pressure of 0.3 Pa and substrate temperature of 250 °C. The results of further structure analysis show that the interplanar spacings d are enlarged in other directions besides the direction perpendicular to the substrate. Apart from the film stress, the doping concentration and the doping site of Al play an important role in the variation of lattice parameters. When the doping concentration of Al is more than 1.5 wt.%, part of Al atoms are incorporated in the interstitial site, which leads to the increase of lattice parameters. This viewpoint is also proved by the first principle calculations.     

Ag/PEO nanocomposite fabricated in a planar magnetron sputtering

Thin films of silver (Ag)/polyethylene-oxide (PEO) nanocomposite were fabricated by a co-deposition of Ag sputtering particles and PEO thin film on substrates using a planar magnetron sputtering system. The PEO were polymerized from the monomer ethyl glycol dimethyl ether in the magnetron sputtering (MS) plasma. The nanocomposites were characterized by using UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The correlation was performed between the concentrations of Ag and functional group density in Ag/PEO nanocomposites with the discharge parameters, such as sputtering gas pressure and the distance of target-to-substrate. By using AFM and XRD, it is illustrated that the Ag particles distribute uniformly in the body of nanocomposite and remain in atomic status with preferential growth in facet of (111).