Reactive Ion Beam Sputtering Research Articles

Structure and photoluminescence properties of SiCN films grown by dual ion beam reactive sputtering deposition

Silicon carbide nitride (SiCN) films were deposited on p-Si (100) substrates by dual ion beam reactive sputtering deposition with various assisting ion beam energies at room temperature. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and Raman scattering measurement were used to investigate the properties of the films. Results show that an increase in assisting ion beam energy remarkably influences film composition. The effects of assisting ion beam energy on chemical structure and photoluminescence properties and their interplays in SiCN films are discussed in detail.

The Effect of Faraday Rotation Enhancement in Nanolayered Structures of Bi - Substituted Iron Garnets

The effect of considerable enhancement of Faraday rotation (FR) and figure of merit (Q) in Bi, Gd, Al-substituted iron garnets plus Bi2O3 (Bi, Gd, Al: YIG / Bi2O3) nanocomposite films on Gd3Ga5O12 (GGG) substrates was found. It reached threefold enhancement of the FR and twofold of the Q one. These films were produced by reactive ion beam sputtering of appropriate targets and following separate annealing. In addition it was determined that in double layer Bi-substituted yttrium iron garnet (Bi: YIG) nanostructures on GGG substrates the upper layer (0.5 – 3.0 nm) considerably affects the magneto-optical properties of the “thick” (8.0 – 10.0 nm) bottom layer. The possible reasons of these effects are discussed.

Tungsten-doped vanadium dioxide thin films on borosilicate glass for smart window application

Tungsten-doped VO2 (W–VO2) thin films with low metal–semiconductor transition temperature (Tt) of 34°C were grown on borosilicate glass substrates by reactive ion beam sputtering at room-temperature (RT) followed by a post annealing process. In order to investigate the thermal process effect, four samples S1–S4 were annealed at different temperatures of 490, 530, 570 and 610°C, respectively. X-ray photoelectron spectroscope and Raman measurements demonstrate that the tungsten atoms have been successfully doped into VO2 films. Unlike VO2 thin films which should be annealed at critical temperature, well crystallized W–VO2 films can be annealed in a wide temperature range, i.e. 530–570°C, as revealed by both electrical and optical property investigations. Besides, the infrared (IR) transmittance measured below/above Tt illustrates that W–VO2 films possess excellent switching efficiency, i.e. 33% at 2500nm for S3. Above all, the near RT phase transition, RT deposition, easy control of annealing process and high IR switching efficiency make the W–VO2 thin film a promising material for application of smart windows.

Thin Film Materials for Optical Interference Filters

Abstract. Microstructural, optical and mechanical properties of oxide and fluoride films are examined. Superior optical quality, durability and environmental stability are achieved for oxides deposited by ion assist reactive ion beam sputtering and thermal evaporation. The materials and deposition techniques are discussed with regards to manufacturing of optical interference filters for near-UV – mid-IR wavelengths. High performance of thin film materials and optical filters is demonstrated.

Influence of Oxygen to Argon Ratio on the Structural and Morphological Properties of Nb-Doped SrTiO<sub>3</sub> Epitaxial Films Grown by Reactive Ion Beam Sputter Deposition

Nb-doped SrTiO3 (STNO) films were grown on (001)-oriented LaAlO3 substrates by a reactive ion beam sputter deposition at various mixing ratios (OMRs) with a substrate temperature of 800oC. The STNO films exhibited good crystallinity with an epitaxial orientation as characterized by high-resolution X-ray diffraction, grazing-incidence X-ray diffraction, and in-plane pole figure analysis. A decrease of out-of-plane and in-plane lattice constants was observed with an increase of OMR. The surface morphology of the STNO films showed a very dense fine-grain structure. The root-mean-square roughness was found to be increased as the OMR increased. Moreover, the elemental compositions of the STNO films were examined by X-ray photoelectron spectroscopy.

Nanostructured vanadium oxide thin film with high TCR at room temperature for microbolometer

In order to obtain high quality of thermal sensitive material, VOx thin film of high temperature coefficient of resistance (TCR) of 6.5%/K at room temperature has been deposited by reactive ion beam sputtering and post annealing method. AFM and XRD measurements indicate that the VOx thin film with nanostructured crystalline is composed of VO2 and V2O3. The nanostructured VOx microbolometer has been designed and fabricated. The measurement of the film system with TiN absorbing layer indicates that it has about 92% infrared absorption in the range of 8–14μm. The performance of this bolometer, comparing with that of bolometer with common VOx, has a better result. At 20Hz frequency and 10μA bias current, the bolometer with high TCR has reached detectivity of 1.0×109cmHz1/2/W. It also indicates that this nanostructured VOx thin film has not only a higher TCR but also a lower noise than common VOx thin film without annealing.

Vanadium Oxide Thin Films Synthesized by Reactive Ion Beam Sputter Deposition: Influence of Processing Parameters

Vanadium oxide thin films were deposited by reactive ion beam sputtering deposition onto glass substrates. The films were prepared by sputtering from a metallic vanadium target with an argon+oxygen ion beam in vacuum. Different processing conditions were evaluated with focus in obtaining monoclinic VO2(M) phase, which is known to exhibit a semiconducting-metal phase transition near room temperature. X-ray diffractometry (XRD) analyses revealed amorphous films for temperatures below 500°C. In crystalline films, the co-existence of VO2(M) with other phases was suppressed by pre-depositing a very thin metallic vanadium seeding layer which showed to promote the formation of single phase VO2(M) films. The VO2(M) films showed clearly the distinctive optical modulation behavior at the near-infrared range when going through the phase transition. The temperature dependence of sheet resistance supports the optical analyses revealing an evident semiconducting-metal behavior change up to over 2 orders of magnitude.

Characterization of nitrogen doped p-type ZnO thin films prepared by reactive ion beam sputter deposition

Nitrogen doped ZnO (ZnO:N) thin films have been successfully prepared by reactive ion beam sputter deposition. The ZnO:N thin films show a preferred growth orientation along the (002) direction regardless of nitrogen flow rates. Raman spectroscopy analysis shows nitrogen related local vibration modes at 275 and 576cm−1 in addition to the ZnO E2 (high) mode at 436cm−1, indicating a successful incorporation of nitrogen into the ZnO. Both of the peak intensities of 275 and 576cm−1 reach a maximum after post-growth annealing at 500°C. ZnO:N deposited with a 0.5sccm nitrogen flow rate exhibits p-type conductivity with a hole concentration of 2.1×1017/cm3 and a mobility of 3cm2V−1s−1 after annealing at 500°C. Conversion to p-type conductivity was not observed on ZnO:N deposited with higher nitrogen flow rates. The p-type conductivity remains stable after it was stored at ambient conditions for more than two months. The p-type ZnO:N thin film is transparent in the visible range with a transmittance larger than 83%. SIMS analysis indicates that nitrogen concentration of less than 1.2at.% results in the successful preparation of p-type ZnO:N. ZnO:N deposited with higher nitrogen concentration results in n-type conductivity which is likely due to the formation of molecular nitrogen replacing oxygen sites that act as double donors (N2)O.

Low transition-temperature characteristic in VOx films grown on Si3N4/Glass substrates

VOx thin films grown on a borosilicate glass substrate with a Si3N4 buffer layer by reactive ion beam sputtering with the varying substrate temperature, argon and oxygen (Ar/O2) gas mixture ratio and annealing temperature are investigated. The XRD patterns show that the films are composed of different vanadium oxides, such as V2O3, VO2, V6O13 and V2O5. The electrical resistance tests indicate that the films' phase transition temperature rises (from 29 to 35°C) as the substrate temperature increases (from 250 to 310°C). Besides, change of the Ar/O2 gas mixture ratio has a huge impact on the films' transition temperature and switching efficiency. VOx thin films fabricated with an Ar/O2 gas mixture ratio of 60:20, 60:30 and 60:40SCCM exhibit a phase transition feature at a temperature of 36, 30 and 32°C, respectively. The VOx thin films show a phase transition character at a temperature of 35, 30 and 34°C, respectively, as the annealing temperature increases from 400 to 460°C with an increment of 30°C. Additionally, the switching efficiency of sample 6 is the lowest owing to the annealing temperature which is too low to make the film oxidized completely.

Reduction in anti-ferromagnetic interactions in ion-beam deposited Fe3O4 thin films

Phase pure Fe3O4 thin films of thickness ∼42 nm have been prepared on the Si(100) substrate by reactive ion beam sputtering in the growth temperature range of 150–250 °C. A high degree of phase purity in the 175 °C sample has been confirmed by the XRD, Raman shift, and R-T measurements. The polycrystalline films show a sharp Verway transition as supported by temperature dependent resistivity, AC susceptibility, and coercivity behavior. The significant feature of these films is the early saturation of their room temperature magnetization at ∼400 mT, indicating the presence of low anti-ferromagnetic competitions in sharp contrast to most of the previous reports. The noticeable reduction of anti-phase boundaries and its dependence on growth temperature has been correlated with the energetic ion-beam deposition process, and explained in terms of the of ionic vacancy migration approach of Eerenstein et al. [Phys. Rev. B 68, 014428 (2003)]. The electronic conduction of these films is governed by near-neighbor hopping above 240 K and Shklovskii-Efros variable range hopping below this transition temperature.

Bi-substituted iron garnet films for one-dimensional magneto-photonic crystals: Synthesis and properties

The crystallization processes in Bi2.8Y0.2Fe5O12, Bi2.5Gd0.5Fe3.8Al1.2O12, Bi1.5Gd1.5Fe4.5Al0.5O12 and Bi1.0Y0.5Gd1.5Fe4.2Al0.8O12 garnet films deposited by reactive ion beam sputtering on (111) gadolinium–gallium garnet substrates, optical glass-ceramic and SiO2 films have been studied. Films were annealed at low pressure in oxygen atmosphere and in the air. The possibility of preparation of crystalline garnet films with high concentration of bismuth on the SiO2 films using a buffer layer with low concentration of Bi has been shown. This allows to produce one-dimensional magneto-photonic crystals with high effective Faraday rotation (several tens of°/μm for the visible optical spectrum).

Optical nonlinearities of nanostructured VO2 thin films with low phase transition temperature

Vanadium dioxides (VO2) thin films which change from a monoclinic semiconductor phase to a tetragonal metallic structure at the temperature of 29°C have been fabricated by reactive ion beam sputtering. Micrograph of scanning electron microscope (SEM) shows that the grain size of VO2 crystallite ranges from 20nm to 50nm. Regeneratively amplified Ti:sapphire laser pulses were applied to induce the phase transition, which was accompanying with the third-order optical nonlinearities in VO2 thin films. Open-aperture and closed-aperture measurements of Z-scan were used to study the optical absorptive and refractive nonlinearities. Nanostructured VO2 thin films exhibit two-photon absorption and a negative nonlinear index of refraction when phase transition is induced. The optical nonlinearities are due to excitation of electronic subsystem only and without involving of the structural semiconductor-to-metal phase transition.

反応性イオンビームスパッタリングによるCoFe<SUB>2</SUB>O<SUB>4</SUB> (100)配向膜の作製

反応性イオンビームスパッタリングによるCoFe<SUB>2</SUB>O<SUB>4</SUB> (100)配向膜の作製

Effect of nanoscale ripples on the formation of ZnO quantum dots

Nano-scale ripples on Si (100) substrates were prepared by argon ion beam sputtering at 6, 8, and 10 keV with an ion fluence of 5 × 1017 ions/cm2. The spatial wavelength of the nano-scale ripple increases as the ion beam energy increases, regardless of ion beam incident angles, indicating that ion beam induced diffusion is the dominant diffusion mechanism. ZnO quantum dots (QDs) with diameters less than 20 nm and heights less than 4 nm can be prepared over the temperature range from 200 ∼ 300 °C by reactive ion beam sputter deposition. Compared with ZnO QDs deposited on Si substrates without nano-scale ripple, the ion-beam textured substrate provides a wider processing window, improved dot size, and increased QD density.

Influence of substrate crystallography on the room temperature synthesis of AlN thin films by reactive sputtering

A pulsed DC reactive ion beam sputtering system has been used to synthesize aluminium nitride (AlN) thin films at room temperature by reactive sputtering. After systematic study of the processing variables, high-quality polycrystalline films with preferred c-axis orientation have been grown successfully on silicon and Au/Si substrates with an Al target under a N 2/(N 2 + Ar) gas flow ratio of 55%, 2 mTorr processing pressure and keeping the temperature of the substrate holder at room temperature. The crystalline quality of the AlN layer as well as the influence of the substrate crystallography on the AlN orientation has been characterized by high-resolution X-ray diffraction (HR-XRD). Best ω-FWHM (Full Width at Half Maximum) values of the (0 0 0 2) reflection rocking curve in the 1 μm thick AlN layers are 1.3°. Atomic Force Microscopy (AFM) measurements have been used to study the surface morphology of the AlN layer and Transmission Electron Microscopy (TEM) measurements to investigate the AlN/substrate interaction. AlN grew off-axis from the Si substrate but on-axis to the surface normal. When the AlN thin film is deposited on top of an Au layer, it grows along the [0 0 0 1] direction but showing a two-domain structure with two in-plane orientations rotated 30° between them.

Electrical and gas-sensitive properties of nanostructured SnO2:ZrO2 semiconductor films

The results of a study of the effect of atomic composition of metal-oxide semiconductor composites SnO2:ZrO2 on the surface morphology, polycrystal grain size, resistivity, concentration, free-carrier mobility, and gas-sensitive properties of thin films (0.5–2.5 μm) are presented. Films SnO2 with ZrO2 additives (the Zr content was varied from 0.5 to 4.6 at %) are grown by reactive ion-beam sputtering of metal targets of different compositions in a controlled Ar + O2 atmosphere. Using transmission electron microscopy, atomic-force microscopy, and high-resolution transmission electron microscopy, it is experimentally shown that, as the Zr content increases in the SnO2:ZrO2 film composition, the polycrystal grain size decreases from 45 to 10 nm, the free-carrier concentration decreases almost by four orders of magnitude and the mobility increases by approximately nine times. As the Zr content increases in the SnO2:ZrO2 film from 0.5 to 4.6 at %, the temperature of maximum gas sensitivity of films to such gases as ethanol, isopropyl alcohol, and acetone decreases by 100–190°C.

Growth of ZnO quantum dots on Si nano ripples

Substrates with nano-scale ripples are excellent templates for the deposition of semiconductor nanostructures. We have prepared quasi periodical nano-scale ripples on Si (100) substrates with spatial wavelength λ from ~ 70 to ~ 150 nm by ion beam sputtering. ZnO QDs with diameters from 17 to ~ 30 nm and heights from 2 to ~ 4 nm have been successfully deposited by reactive ion beam sputter deposition. The QD size and distribution were found to be dependent both on growth conditions and spatial wavelength of the nano-scale ripple. On substrates with λ ~ 150 nm, ZnO QDs were distributed evenly across the wafer, while on substrates with λ ~ 70 nm, ZnO QDs were preferentially located along the crest of the nano-scale ripples. As the QD height decreases from ~ 4 to 2 nm, room temperature photoluminescence UV emission energy blue shifts by 80 meV. Possible sources of the blue shift are presented.

Vanadium dioxide thin film with low phase transition temperature deposited on borosilicate glass substrate

A nanostructured vanadium dioxide (VO 2) thin film showing a low metal-insulator transition temperature of 30 °C has been fabricated through reactive ion beam sputtering followed by thermal annealing. The thin film was grown on borosilicate glass substrate at the temperature of 280 °C with a Si 3N 4 buffer layer. Both scanning electron microscopy and atomic force microscopy images have been taken to investigate the configuration of VO 2 thin film. The average height of the crystallite is 20 nm and the grain size ranges from 40 nm to 100 nm. The transmittance measured from low to high temperatures also reveals that the film possesses excellent switching property in infrared light at critical transition temperature, with switching efficiency of 52% at 2600 nm. This experiment paves the way of VO 2 thin film's application in smart windows.

The Effect of Ion-Beam Treatment on TiO2Coatings Deposited on Polycarbonate Substrates

The effect of an Ar plasma treatment on polycarbonate substrates was investigated using <TEX>$TiO_2$</TEX> coatings produced by reactive ion-beam assisted sputtering. The typical pressure used during sputtering was about <TEX>$10^{-4}$</TEX> Torr. After the Ar plasma treatment, the contact angle of a water droplet was reduced from <TEX>$88^{\circ}$</TEX> to <TEX>$52^{\circ}$</TEX> and then further decreased to <TEX>$12^{\circ}$</TEX> with the addition of oxygen into the chamber. The surface of the polycarbonate substrate hanged from hydrophobic to hydrophilic with these treatments and revealed its changing nano-scale roughness. The <TEX>$TiO_2$</TEX> films on the treated surface showed various colors and periodic ordering dependant on the film thickness due to optical interference.

Cooperative upconversion and optical gain in ion-beam sputter-deposited Er_xY_2-xSiO_5 waveguides

Single-phase, polycrystalline Er(x)Y(2-x)SiO(5) thin films were deposited by reactive ion-beam sputter deposition and rapid thermal annealing. Due to the crystalline nature, the silicate thin films provide peak Er(3+) emission cross-section of 0.9 +/- 0.02 x 10(-20) cm(2) that is higher than that in silica. Optical gain, with near 60% inversion, is achieved via optical pumping of a single-mode, ridge-type waveguide with the silicate core with an Er concentration of 1.7 x 10(20) cm(-3). Analysis of pump-power dependence of the optical gain and spontaneous emission intensity of Er(3+) indicate that the gain is limited by cooperative upconversion process, whose coefficient is determined to be (8 +/- 3) x 10(-17) cm(3)/sec.