Dual Ion Beam Sputtering Deposition Research Articles

Effect of oxygen flow on the optical properties of hafnium oxide thin films by dual-ion beam sputtering deposition

Effect of oxygen flow on the optical properties of hafnium oxide thin films by dual-ion beam sputtering deposition

Plasmonic characteristics of niobium nitride thin films modulated by assisting ions

NbNx films were prepared by dual ion beam sputter deposition. Different assisting ion current density Ja and assisting ion energy Ea were used to modulate the structural and dielectric properties of the films. All the films are of fcc structure, and assisting ions can improve their crystallinity. Higher Ja and Ea can reduce the screened plasma frequency and the optical energy loss of the films. Importantly, with appropriate experimental parameters, the NbNx films exhibit tunable dual epsilon-near-zero behavior. The assisting ions cause the variation of the carrier concentration in the films, and then modulate the dielectric properties of the films. Our results show that NbNx films can be applied in different fields by tailoring their plasmonic properties by assisting ions.

Optimization of dielectric films with dual ion beam sputtering deposition for high reflectivity mirrors

Abstract Dielectric thin films deposited by Ion beam sputtering deposition technique have superior properties of good adhesion and customized optical properties suits to many optical filters for electro-optical sensors. In the present work Tantalum Pentoxide (Tantala) and Silicon Dioxide (Silica) thin films are fabricated with dual ion beam sputtering deposition process. The process parameters are optimized to achieve better surface quality and optical constants. The effect of the assist ion beam on the film properties is evaluated. Multi-layer dielectric mirrors realized with 1000 ppm loss on optimization of single-layer Silica and Tantala films, which will be suitable for linear and Ring Laser Resonators. The films are characterized by ellipsometer, non-contact optical profiler, spectrophotometer, and cavity ring-down loss meter. The multi-layer mirrors were subjected to vacuum annealing and the effect of annealing on film reflectivity is evaluated. The work emphasizes the process requirements of Ion Beam Sputtering to realize high reflectivity and low loss mirrors of Tantala and Silica films from Ta2O5 and SiO2 target materials. It gives an insight into the process deficiencies in matching the theoretical design of multi-layer mirrors from the practical aspects of coatings.

Microstructure and Young's modulus of ZrN thin film prepared by dual ion beam sputtering deposition

The ZrN film has drawn wide attentions as a protective material due to its attractive properties. In this study, ZrN films having thickness about 45 nm were prepared by dual ion beam sputtering deposition to investigate the influence of assisted ion beam (300 eV/25 mA ~ 800 eV/60 mA) and deposition temperature (unheated ~ 600 °C) on nano-film microstructure, grain size, density, and Young's modulus. A double layer structure, comprising an amorphous layer closed to the substrate and a crystalline layer above the amorphous layer was observed. The amorphous layer thickness decreases with the increase of atom mobility and the decrease of oxygen concentration. The assisted ion beam flux and energy influence the grain size, density, and Young's modulus. A porous structure and rough surface forms under high flux and energy assisted ion beam due to the severe damage and resputtering under high-energy nitrogen ion. Besides this, thickness of the amorphous layer decreases, increasing the grain size, density, and Young modulus due to deposition temperature. The Young's modulus shows some dispersion in the low (111) texture coefficient region indicates excellent linearity with the grain size and density. The Young modulus of nanofilm is strongly influenced by grain size or density. The nanofilm texture shows negligible impact on thin film Youngs Modulus.

Dual ion beam grown silicon carbide thin films: Variation of refractive index and bandgap with film thickness

Amorphous SiC thin films on a silicon substrate (Si) with different film thicknesses (about 20–450 nm) were deposited using dual ion beam sputtering deposition (DIBSD) at room temperature. These SiC thin films were of high quality showing high coverage (>90%) and low surface and interface roughness (<5 Å). The structure and morphology of these SiC/Si systems were explored by x-ray reflectivity, x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The bonding configuration and compositional details of the SiC films were examined by Fourier-transform infrared and Raman spectroscopy. The optical constants (complex dielectric function and refractive index) and the bandgap of SiC thin films were analyzed through spectroscopic ellipsometry in the 0.55–6.3 eV energy range. An increase in the bandgap (5.15–5.59 eV) and a corresponding decrease in the refractive index (2.97–2.77) were noticed with the increase of SiC film thickness from about 20–450 nm. This thickness dependent trend in optical properties is attributed to the increase of the C to Si atomic concentration ratio in DIBSD grown SiC thin films with increasing film thickness, as observed from energy dispersive x-ray analysis measurements. The unique properties of amorphous SiC have already placed it as a suitable candidate for solar cells and photovoltaic applications in its thin film form. The results developed in this study for thickness dependent optical properties of SiC thin films can be used for further optimizing the performance of SiC in various applications through tuning of optical properties.

AMORPHIZATION OF CERIUM MONONITRIDE DURING OXIDIZATION CHARACTERIZED BY OPTICAL MICROSCOPY, SCANNING ELECTRON MICROSCOPY, X-RAY DIFFRACTION AND X-RAY PHOTOELECTRON SPECTROSCOPY

Cerium mononitride (CeN) film was fabricated by dual ion beam sputtering deposition method on silicon wafer. The oxidization process of CeN film was monitored by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that, when the CeN film was exposed to ambient atmosphere, bubbles appeared on the film surface rapidly and then the surface flaked off to powders. Meanwhile, the CeN film changed from polycrystalline to amorphous. XPS analysis indicated that the CeN was oxidized to Ce2O3 initially, and then further oxidized to CeO2. These results indicated that the CeN film degraded easily in ambient atmosphere, exhibiting little or no passivation.

Microstructure evolution and Young's modulus of He-implanted nanocrystalline tungsten film

Nanocrystalline tungsten has been widely investigated due to its excellent irradiation resistance. In this study, the microstructure and related Young's modulus of nanocrystalline tungsten film prepared by dual ion beam sputtering deposition and subsequently irradiated by 30 keV He+ of varying fluences at room temperature have been studied by experimental and simulation methods. The mean He bubble size is about 0.7 nm, and the implanted He is preferred to be trapped by the grain boundaries. Few He bubbles are formed nearby the high density defect regions due to more trapping sites for He atoms. The lattice swelling increases with the increase of He fluence. The Young's modulus of the films was measured by LAwave, which indicates the Young's modulus decreases with the increase of He fulence. Molecular dynamics simulations are performed to explore the dependence of Young's modulus on the swelling and the properties of He bubbles. The results indicate that the lattice swelling has a limited influence on Young's modulus. The concentration of He is confirmed to seriously affect the Young's modulus after He implantation. With the same concentration of He atoms, the distribution of He bubbles is a key factor on tensile strength. The He bubbles at grain boundary have a stronger influence on the tensile strength than that in grain interior. He bubbles with higher He/V ratios affect more significantly on the mechanical properties. All these results provide new understandings for radiation damages of nano-materials used in reactors.

Deposition of thin tungsten carbide films by dual ion beam sputtering deposition

Hard materials coating fabricated by physical vapor deposition techniques methods are wildly used because of their excellent mechanical strength, stability and chemical resistivity. In this article, compact and high Young's modulus tungsten carbide films with ∼100 nm thickness were prepared on Si (100) substrates by dual ion beam sputtering deposition method, and elucidates the influence of deposition temperature and assistant ion source on the adhesion strength and Young's modulus of tungsten carbide thin films. Morphological analysis, composition, and structure of tungsten carbide films were investigated by Atomic force microscope, X-ray photoelectron spectrometry, Scanning electron microscope. The X-ray diffraction analysis shows that the thin films comprise of hexagonal structure W2C. The adhesion strength is improved due to ion beam source bombardment and elevated deposition temperature. The Young's modulus of the film is codetermined by the density, microstructure and crystal structure. The influence of density, microstructure and crystal structure on Young's modulus was discussed in detail. The Young's modulus is improved due to the more compact structure caused by appropriate assistant source bombardment and elevated deposition temperature, and gets degradative due to the disorganized, coarse and granular structure caused by overlarge assistant source bombardment.

Phase control and Young’s modulus of tungsten thin film prepared by dual ion beam sputtering deposition

In this letter, tungsten films of varying thickness from ∼20 nm to ∼80 nm were prepared at different deposition temperature by Dual ion beam sputtering deposition (DIBSD) method. The influence of thickness and deposition temperature on the films phase, microstructure and Young’s modulus was studied briefly. The experiments prove that a double-layer structure, formation takes place i.e. β phase tungsten layer (low crystallinity) forms adjacent to the substrate and α tungsten phase layer (high crystallinity) forms above β phase. The increase in both the thickness and deposition temperature promotes the transformation from β phase to α phase which initiates from the interface between two phases. There is a critical thickness of ∼20 nm below which the film is a pure β phase, and the minimum thickness of forming pure α phase is affected by the deposition temperature, with 74 nm at 450°C, and 58 nm at 600°C. Furthermore, the decrease Young’s modulus of the tungsten film is ascribed to the formation of β phase which possesses low crystallinity with low density.

Corrosion resistance and mechanism of CeN, TiN and CeN/TiN bilayer composite film deposited by dual ion beam sputtering

Uranium (U) is an important engineering material in nuclear energy industry. Its environmental instability, however, posed challenges on its applications. Due to the active property and similar electronic configuration, Cerium (Ce) can be used as a reference metal to simulate the protection of uranium from corrosion. In order to improve the corrosion resistance of Ce, ceramic CeN, and ceramic TiN and CeN/TiN bilayer composite film were prepared by dual ion beam sputtering deposition system (DIBD). The crystal structure of films was identified by X-ray diffraction (XRD) and the chemical states of CeN film were characterized by the X-ray photoelectron spectroscopy (XPS). The Surface morphology and structure changes in atmospheric environment were examined by scanning electron microscopy (SEM) and XRD, The corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental results indicate the single film of CeN or TiN shows poor corrosion resistance, but the CeN/TiN bilayer composite film has better corrosion resistance. Based on the XPS, SEM and impedance analysis, we supposed that the loose of integrity and passivity breakdown on as deposited coating may be the corrosion inducement.

Trap assisted charge multiplication enhanced photoresponse of Li–P codoped p-ZnO/n-Si heterojunction ultraviolet photodetectors

In this work, we report a high-performance p-ZnO/n-Si heterojunction-based ultraviolet (UV) photodetector fabricated by dual ion beam sputter deposition. The lithium–phosphorus (Li–P) codoping route was used to realize low resistive and stable p-type ZnO. The current–voltage characteristics of p-ZnO/n-Si heterojunction photodiode showed good rectifying behavior with a rectification ratio of 170 at ±3 V. The spectral response measurements of the photodiode showed excellent responsivity with a peak observed around ~325 nm and cutoff wavelength around 370 nm. The maximum responsivity achieved was 2.6 A W−1 at an applied reverse bias of −6 V. The external quantum efficiency determined was of the order of ~1000% which is attributed to the trap assisted multiplication of charge carriers.

Room temperature blue LED based on p-ZnO/(CdZnO/ZnO) MQWs/ n-ZnO

Blue multiple quantum well light-emitting diodes comprising of p-ZnO/(Cd0.12Zn0.88O/ZnO) multiple quantum wells/n-ZnO were grown on n-Si substrates using dual ion-beam sputtering deposition technique. X-ray diffraction of individual thin films revealed growth preferentially in c-axis direction perpendicular to the substrate. Photoluminescence studies indicated blue emission ~ 440nm from CdZnO and UV emission ~384nm arising from ZnO thin films. The LED showed a rectifying current–voltage behavior with a turn-on voltage of ~4.69V at room temperature. It emanated a room-temperature electroluminescence peak centered at 442nm, along with shoulder peak at 380nm in ultra-violet region associated with the recombination in ZnO layers of structure. It was found that with the increase in injection current the blue EL intensity increased and UV emission decreased, leading to improvement in successful radiative recombination in quantum wells. The results indicate prospects of fabrication of ZnO-based blue multiple quantum well LEDs.

High temperature sensors fabricated on Al2O3 ceramic and nickel-based superalloy substrates

The main purpose of this study is to develop resistance temperature sensors which can work at high temperature. A 2μm thick Al2O3 thin film was deposited as an electrical insulating film on Pt-coated Al2O3 ceramic substrates and nickel-based superalloy substrates by Dual Ion Beam Sputtering Deposition (DIBSD). The results of atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photon electron spectroscopy (XPS) analyses reveal that the Al2O3 films were dense, smooth and pinholes free with roughness around 3nm. The vertical electrical resistance of thin films deposited on Pt-coated Al2O3 ceramic substrates was more than 2GΩ at room temperature and 100kΩ even at around 800°C. Both resistance temperature sensors (RTSs) fabricated on Al2O3 ceramic substrate and that on nickel-based superalloy substrates showed a linear relation up to 1000°C. The RTS on the ceramic substrates showed stable after 4 thermal cycles while RTS on the superalloy substrates showed a good repeatability of heating and cooling curves even after experiencing a high temperature environment as high as 1000°C.

Preparation, characterization and application of high-temperature Al2O3 insulating film

Abstract NiCoCrAlY coatings were deposited on nickel-based superalloy by magnetron sputtering. The thermally grown oxide (TGO) layer of aluminum oxide (α - Al 2 O 3 ) was formed on the surface of the NiCoCrAlY coating by heat treatment at 950 °C in an Ar atmosphere followed by subsequent thermal oxidation in air at 1100 °C. Another 2 μm thick Al 2 O 3 film was deposited on the TGO layer by dual ion beam sputtering deposition (DIBSD) to further improve insulation resistance at high temperature. The effect of thermal oxide time on the morphology and microstructure of the TGO layers was investigated by SEM, XRD and XPS techniques. It's indicated that excessive thermal oxidation would produce NiO in the TGO layer, which was harmful to the high-temperature insulating property of TGO layer. The stoichiometric ratio Al/O for the sputtered Al 2 O 3 film was close to 2:3. The electrical resistance of the insulating film was measured at 200 °C–800 °C. The result showed that the insulating Al 2 O 3 film including TGO layer and sputtered Al 2 O 3 layer had a good insulating property at high temperature. Finally, a thermal resistance temperature sensor was prepared on the surface of the Al 2 O 3 film insulating film to verify its electrical insulating property.

Bias-dependent photo-detection of dual-ion beam sputtered MgZnO thin films

The structural, morphological, elemental and electrical properties of MgZnO thin films, grown on p-Si (001) substrates by dual-ion beam sputtering deposition (DIBSD) system at different substrate temperatures were thoroughly investigated. X-ray diffraction (XRD) pattern of MgZnO film exhibited crystalline hexagonal wurtzite structure with the preferred (002) crystal orientation. The full-width at half-maximum of the (002) plane was the narrowest with a value of 0.226° from MgZnO film grown at 400°C. X-ray photoelectron spectroscopy analysis confirmed the substitution of Zn2+ by Mg2+ in MgZnO thin films and the absence of MgO phase. Correlation between calculated crystallite size, as evaluated from XRD measurements, and room-temperature carrier mobility, as obtained from Hall measurements, was established. Current–voltage characteristics of MgZnO thin films were carried out under the influence of dark and light illumination conditions and corresponding values of photosensitivity were calculated. MgZnO film grown at 100°C exhibited the highest photosensitivity of 1.62. Compared with one of the best-reported values of photosensitivity factor from ZnO-material-based films available in the literature, briefly, ∼3.085-fold improved photosensitivity factor at the same bias voltage (2 V) was obtained.

Room temperature synthesis of boron nitride thin films by dual-ion beam sputtering deposition

Boron nitride (BN) films are prepared by dual-ion beam sputtering deposition at room temperature (~25°C). An assisting argon/nitrogen ion beam (ion energy Ei=0–300eV) directly bombards the substrate surface to modify the properties of the BN films. The effects of assisting ion beam energy on the characteristics of BN films were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectra, atomic force microscopy, and optical transmittance. The density of the B–N bond in the film increased with the increase in assisting ion beam energy. The highest transmittance of more than 95% in the visible region was obtained under the assisting ion beam energy of 300eV. The band gap of BN films increased from 5.54eV to 6.13eV when the assisted ion-beam energy increased from 0eV to 300eV.

Room temperature ppb level H2S detection of a single Sb-doped SnO2 nanoribbon device

Sb-doped SnO2 nanoribbons (NRs) with a single crystal structure are synthesized via thermal evaporation. H2S gas sensor is developed based on a single Sb-SnO2 NR through dual-ion beam sputtering deposition with a mask template. The response of the Sb-SnO2 NR sensor has been measured up to 56–100ppm of H2S at 150°C. More importantly, this sensor shows a response of 10(1.6) toward 100ppb of H2S at 150°C(25°C), which promotes the detection limit of H2S. The NR-based sensor also exhibits a high sensitivity, good selectivity and long-term stability with a prompt response time, demonstrating good sensing capabilities at room temperature. The mechanism for enhanced sensing performance of Sb-doped SnO2 nanoribbon is discussed.

Spetroscopic ellipsometry study on electrical and elemental properties of Sb-doped ZnO thin films

Room-temperature spectroscopic ellipsometry data has been analyzed to determine the complex dielectric functions, ɛ(E) = ɛ1(E) + iɛ2(E) of as-deposited Sb-doped ZnO (SZO) thin films grown on n-Si(100) substrates by dual ion beam sputtering deposition system for different growth temperatures (Tg). The dielectric functions have been obtained from ellipsometry data analyses using Cody-Lorentz oscillator in the GenOsc model. A gradual reduction in the value of electron concentration and finally the conversion of doping characteristics from donor type to acceptor type was observed with the rise in Tg. This, in turn, resulted in the decline of broadening of ɛ1 peaks, and hence in the increase of excitonic lifetime. Optical band-gap energy was observed to decrease with increase in Tg from 200 to 300 °C, and then rise continuously with further increase in Tg. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. Hall measurement and X-ray photoelectron spectroscopy analysis confirmed that the change in the electrical conduction from n-to p-type was due to the enhancement in the value of Sb5+/Sb3+ ratio and SbZn–2VZn complex formation in SZO films.

Blue electroluminescence from Sb-ZnO/Cd-ZnO/Ga-ZnO heterojunction diode fabricated by dual ion beam sputtering.

p-type Sb-doped ZnO/i-CdZnO/n-type Ga-doped ZnO was grown by dual ion beam sputtering deposition system. Current-voltage characteristics of the heterojunction showed a diode-like rectifying behavior with a turn-on voltage of ~5 V. The diode yielded blue electroluminescence emissions at around 446 nm in forward biased condition at room temperature. The emission intensity increased with the increase of the injection current. A red shifting of the emission peak position was observed with the increment of ambient temperature, indicating a change of band gap of the CdZnO active layer with temperature in low-temperature measurement.

Influence of annealing temperature on ZnO thin films grown by dual ion beam sputtering

We have investigated the influence of in situ annealing on the optical, electrical, structural and morphological properties of ZnO thin films prepared on p-type Si(100) substrates by dual ion beam sputtering deposition (DIBSD) system. X-ray diffraction (XRD) measurements showed that all ZnO films have (002) preferred orientation. Full-width at half-maximum (FWHM) of XRD from the (002) crystal plane was observed to reach to a minimum value of 0.139° from ZnO film, annealed at 600 °C. Photoluminescence (PL) measurements demonstrated sharp near-band-edge emission (NBE) at ~ 380 nm along with broad deep level emissions (DLEs) at room temperature. Moreover, when the annealing temperature was increased from 400 to 600 °C, the ratio of NBE peak intensity to DLE peak intensity initially increased, however, it reduced at further increase in annealing temperature. In electrical characterization as well, when annealing temperature was increased from 400 to 600 °C, room temperature electron mobility enhanced from 6.534 to 13.326 cm2/V s, and then reduced with subsequent increase in temperature. Therefore, 600 °C annealing temperature produced good-quality ZnO film, suitable for optoelectronic devices fabrication. X-ray photoelectron spectroscopy (XPS) study revealed the presence of oxygen interstitials and vacancies point defects in ZnO film annealed at 400 °C.