Dual Ion Beam Sputtering Research Articles

Influence of in-situ annealing ambient on p-type conduction in dual ion beam sputtered Sb-doped ZnO thin films

Sb-doped ZnO (SZO) films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system and subsequently annealed in-situ in vacuum and in various proportions of O2/(O2 + N2)% from 0% (N2) to 100% (O2). Hall measurements established all SZO films were p-type, as was also confirmed by typical diode-like rectifying current-voltage characteristics from p-ZnO/n-ZnO homojunction. SZO films annealed in O2 ambient exhibited higher hole concentration as compared with films annealed in vacuum or N2 ambient. X-ray photoelectron spectroscopic analysis confirmed that Sb5+ states were more preferable in comparison to Sb3+ states for acceptor-like SbZn-2VZn complex formation in SZO films.

Effect of oxygen partial pressure on the behavior of dual ion beam sputtered ZnO thin films

Undoped ZnO thin films were grown on p-type Si (1 0 0) substrates at different oxygen partial pressure by dual ion beam sputtering deposition system at a constant growth temperature of 400 °C. The crystallinity, surface morphology, optical, elemental and electrical properties of these ZnO thin films was studied. The minimum value of full-width at half-maximum of the θ-rocking curve obtained from x-ray diffraction of the ZnO (0 0 2) plane, was reported to be 0.1865° from ZnO film grown at 50% of (O2/(O2 + Ar))%. Crystalline property of ZnO films was observed to degrade with the increase in oxygen partial pressure. Photoluminescence measurements demonstrated sharp near-band-edge emission at ∼381 nm at room temperature. X-ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies as point defects in ZnO films. Electrical resistivity of ZnO was found to increase with the increase in oxygen partial pressure.

Effect of growth temperature on structural, electrical and optical properties of dual ion beam sputtered ZnO thin films

ZnO epitaxial thin films were grown on p-type Si(100) substrates by dual ion beam sputtering deposition system. The crystalline quality, surface morphology, optical and electrical properties of as-deposited ZnO thin films at different growth temperatures were studied. Substrate temperature was varied from 100 to 600 °C at constant oxygen percentage O2/(O2 + Ar) % of 66.67 % in a mixed gas of Ar and O2 with constant chamber pressure of 2.75 × 10−4 mBar. X-Ray diffraction analyses revealed that all the films had (002) preferred orientation. The minimum value of stress was reported to be −0.32 × 1010 dyne/cm2 from ZnO film grown at 200 °C. Photoluminescence measurements demonstrated sharp near-band-edge emission (NBE) was observed at ~375 nm along with deep level emission (DLE) in the visible spectral range at room temperature. The DLE Peak was found to have decrement as ZnO growth temperature was increased from 200 to 600 °C. The minimum FWHM of the NBE peak of 16.76 nm was achieved at 600 °C growth temperature. X-Ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies point defects in ZnO film grown at 400 °C. The ZnO thin film was found to be highly resistive when grown at 100 °C. The ZnO films were found to be n-type conducting with decreasing resistivity on increasing substrate temperature from 200 to 500 °C and again increased for film grown at 600 °C. Based on these studies a correlation between native point defects, optical and electrical properties has been established.

Mechanical properties and bonding structure of boron carbon nitride films synthesized by dual ion beam sputtering

The BCN films were synthesized on Si (110) wafers by using dual ion beam sputtering deposition from boron carbide target. The influences of ion assist source energy and N2 relative flow rate on the surface roughness, mechanical properties and chemical bonding structure of BCN films were investigated systematically. The surface roughness was measured using non-contact optical surface profilometer and the mechanical properties of BCN films were evaluated with nano-indenter. The BCN films were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the BCN films' surface roughness varied in the range of 5–15 nm, and their hardness and reduced elastic modulus fluctuated in the scope of 18–29 GPa and 192–229 GPa, respectively. When the BCN films' surface roughness varied in the range of 8–12 nm, the values of hardness and reduced elastic modulus were fluctuated slightly. The BCN films with the smoothest surface (Ra = 5 nm) and the highest hardness of 28 GPa were obtained at the ion assist source energy of 200 eV and the N2 relative flow rate of 50%. The BCN films were amorphous and contained several bonding states such as B–N, B–C and C–N with B–C–N hybridization.

Effect of Ta incorporation on the microstructure, electrical and optical properties of Hf1−xTaxO high-k film prepared by dual ion beam sputtering deposition

The microstructure, electrical and optical properties of Hf1−xTaxO (x = 0, 0.18, 0.28, 0.36 and 0.43) high-k thin films deposited by a novel deposition technique—dual ion beam sputtering deposition (DIBSD) have been investigated. From the O1s and Si 2p spectra of X-ray photoelectron spectroscopy (XPS), it is worth noting that the thickness of the interfacial layer significantly decreases after doping appropriate content Ta, and the formation of metal silicate components (M–O–Si) can be effectively suppressed by doping 43% Ta concentration into Hf1−xTaxO system. Compared to the pure HfO2 sample, Hf1−xTaxO with 43% Ta after post-deposition annealing (PDA) exhibits the highest k-value (∼21.0 ± 0.2) and crystallization temperature (950 °C), the smallest root mean square (RMS) surface roughness of Ra ∼ 0.12 nm, Max height–depth Rp−v ∼ 1.5 nm and C–V hysteresis of 50 mV, the lowest leakage current density of 1.13 × 10−8 A/cm2 at Vg=(Vfb−1) and an acceptable value of Eg ∼ 4.68 ± 0.1 eV.

Effect of low energy ion bombardment on structure and photoluminescence characterization of Al-doped ZnO thin films

Al-doped zinc oxide (AZO) films are prepared by dual ion-beam assisted sputter deposition at room temperature. An assisting argon ion beam (ion energy Ei=0–300eV) directly bombards the substrate surface to modify the properties of the AZO films. The effects of assisting ion beam energy on the characteristics of AZO films were investigated based on transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and photoluminescence measurement. With increasing assisting ion beam bombardment, the crystalline quality of the AZO films was improved and the oxygen vacancies were increased observably. Two red emissions originating from the oxygen vacancies in the films appear at 1.71 and 1.64eV. This study suggests that wide-band-gap materials could act as effective visible light emitters and ion beam bombardment provides a simple route to synthesize such materials.

Effect of postdeposition annealing on the structure, composition, and the mechanical and optical characteristics of niobium and tantalum oxide films

Optical, mechanical, and thermal properties of optical thin films are very important for a reliable device performance. In the present work, the effect of annealing on the stability and the characteristics of niobium and tantalum oxide films grown at room temperature (RT) by dual ion beam sputtering were studied. The refractive index (n(λ)), extinction coefficient (k(λ)), hardness (H), reduced Young's modulus (E(r)), and film stress (σ) were investigated as a function of the annealing temperature (T(A)). X-ray diffraction analysis showed that all as-deposited films were amorphous, and crystallization was observed only after annealing at 700°C. Compositional analyses confirmed that the atomic ratio of oxygen to metal in as-deposited and annealed films was close to 2.5, indicating that the films were stoichiometric pentoxides of Nb and Ta. The properties of Nb(2)O(5) and Ta(2)O(5) films were, respectively, affected by postdeposition annealing: n(λ) values (at 550 nm) decreased from 2.30 to 2.20 and from 2.14 to 2.08, the average H and E(r) values increased from 5.6 to 7.4 GPa, and from 121 to 132 GPa for Nb(2)O(5), and from 6.5 to 8.3 GPa, and from 132 to 144 GPa for Ta(2)O(5), and the initial low compressive stress for both materials changed to tensile. We explain the variation of the coating material properties in terms of film stoichiometry, crystallinity, electronic structure, and possible reactions at the film-substrate interface.

X-ray photoelectron spectroscopy and conducting atomic force microscopy investigations on dual ion beam sputtered MgO ultrathin films

Ultrathin films of MgO (~6nm) were deposited on Si(100) using dual ion beam sputtering in different partial pressures of oxygen. These thin films were characterized by X-ray photoelectron spectroscopy (XPS) for chemical state analysis and conducting atomic force microscopy for topography and local conductivity map. No trace of metal Mg was evidenced in these MgO films. The XPS analysis clearly brought out the formation of oxygen interstitials and Mg(OH)2 primarily due to the presence of residual water vapors in the chamber. An optimum value of oxygen partial pressure of ~4.4×10−2Pa is identified with regard to homogeneity of film and stoichiometry across the film thickness (O:Mg::0.93–0.97). The local conductivity mapping investigations also established the film homogeneity in respect of electrical resistivity. Non-linear local current–voltage curves revealed typical tunneling characteristics with barrier width of ~5.6nm and barrier height of ~0.92eV.

On the Electrical and Photoluminescence Properties of Erbium Doped ZnO Thin Film

ABSTRACTEr doped ZnO (Er:ZnO) thin films with Er concentration from 0.1 to 3.6 at. % were prepared by dual beam ion beam sputter deposition at room temperature. Experimental results show that as Er concentration increases from 0.1 to 1.1 at. %, the resistivity of the as-deposited Er:ZnO film decreases from 560 Ω·cm to a minimum of 0.23 Ω·cm, while further increasing Er concentration to 3.6 at. % results in increase of the resistivity to 4.2 kΩ·cm. The as-deposited Er:ZnO with Er concentration of 1.1 at.% also exhibits the highest carrier concentration of 2.3×1019 cm-3. None of the as-deposited Er:ZnO films show 1.5 μm emission without post-growth annealing. Er:ZnO film with Er concentration at 0.5~1.1 at.% shows the strongest 1.5 μm emission after annealing at 700 ~ 900°C, while all the Er:ZnO film becomes semi-insulating after annealing. The discrepancy between the processing conditions for optimized carrier concentration and optimized optically activated Er ions may due to the formation of the pseudo-octahedral structure after annealing that favors the 1.5 μm emission.

The structure and electrical properties of HfTaON high-k films prepared by DIBSD

We have investigated the microstructure and electrical properties of HfTaON high-k films deposited on n-type Si (100) substrate using a dual ion beam sputtering deposition technique (DIBSD). It is worth noting that HfO2 begin to precipitate from four-compound HfTaON and crystallize as a monoclinic phase after annealing at 1100°C. From FTIR spectra, one strong absorption peak at 512cm−1, which is characteristic of the HfO2 monoclinic structure is also observed. The interfacial SiOx can be formed during the annealing procedure rather than sputtering process, and the increase of atomic percentage of SiO bands and transition from SiOx (x<2) to SiO2 are observed with the increase of annealing temperature. High efficiency HfTaON film prepared by novel DIBSD has a higher dielectric constant of 24 and lower leakage current of 2.28×10−8A at Vg=(Vfb−1), as compared with that of SiO2 HfSiON HfTaO films with same thickness.

Preparation of BiFeO3 Thin Films on SrRuO3/SrTiO3(001) Substrate by Dual Ion Beam Sputtering

BiFeO3 (BFO) thin films with various Bi/Fe ratios have been deposited on SrRuO3/SrTiO3(001) substrates by dual ion beam sputtering. A Bi2O3 ceramic disk and an α-Fe2O3 powder disk were used as targets, and simultaneously sputtered using a dual ion beam. Bi/Fe ratio has been controlled by adjusting the beam current ratio on the Bi2O3- and α-Fe2O3-side ion sources. Even a BFO thin film with a Bi/Fe ratio of 0.95 and a smooth surface shows a slightly leaky characteristic. [Fe2+]/([Fe3+]+[Fe2+]) ratio has been estimated by Auger electron spectroscopy (AES). From the AES profiles, the [Fe2+]/([Fe3+]+[Fe2+]) ratio of the BFO thin film with a Bi/Fe ratio of 0.95 is estimated to be 0.14. It is considered that not only improving surface roughness but also enhancing oxidization is important for reduction in leakage current.

Preparation of BiFeO3Thin Films on SrRuO3/SrTiO3(001) Substrate by Dual Ion Beam Sputtering

Preparation of BiFeO₃Thin Films on SrRuO₃/SrTiO₃(001) Substrate by Dual Ion Beam Sputtering

Texture and microstructure evolution in single-phase TixTa1−xN alloys of rocksalt structure

The mechanisms controlling the structural and morphological features (texture and microstructure) of ternary transition metal nitride thin films of the TixTa1−xN system, grown by various physical vapor deposition techniques, are reported. Films deposited by pulsed laser deposition, dual cathode magnetron sputtering, and dual ion beam sputtering have been investigated by means of x-ray diffraction in various geometries and scanning electron microscopy. We studied the effects of composition, energetic, and kinetics in the evolution of the microstructure and texture of the films. We obtain films with single and mixed texture as well as films with columnar “zone-T” and globular type morphology. The results have shown that the texture evolution of ternary transition metal nitrides as well as the microstructural features of such films can be well understood in the framework of the kinetic mechanisms proposed for their binary counterparts, thus giving these mechanisms a global application.

Room temperature deposition of amorphous SiC thin films using low energy ion bombardment

Silicon carbide (SiC) films are prepared by single- and dual-ion beam sputtering deposition at room temperature, respectively. An assisting argon ion beam (ion energy Ei=150 eV) bombards directly the substrate surface to modify the SiC film surface. The thin films are characterized by the Fourier transform infrared spectroscopy (FTIR) and the Raman spectra. With assisting ion beam bombardment, the density of the Si–C bond in the film increases. Meanwhile, the excess carbon or the size of the sp 2 bonded clusters and the amorphous Si ( a-Si) phase decrease. These results indicate that the composition of the films is mainly Si–C bond. UV-vis transmission shows that the E opt increases steadily from 1.85 eV for the amorphous SiC ( a-SiC) films without bombardment to about 2.29 eV for those with assisting ion beam bombardment.

Optical and tribomechanical stability of optically variable interference security devices prepared by dual ion beam sputtering

Optical security devices applied to banknotes and other documents are exposed to different types of harsh environments involving the cycling of temperature, humidity, chemical agents, and tribomechanical intrusion. In the present work, we study the stability of optically variable devices, namely metameric interference filters, prepared by dual ion beam sputtering onto polycarbonate and glass substrates. Specifically, we assess the color difference as well as the changes in the mechanical properties and integrity of all-dielectric and metal-dielectric systems due to exposure to bleach, detergent and acetone agents, and heat and humidity. The results underline a significant role of the substrate material, of the interfaces, and of the nature and microstructure of the deposited films in long term stability under everyday application conditions.

Infrared transition properties of vanadium dioxide thin films across semiconductor-metal transition

Vanadium dioxide thin films were fabricated through annealing vanadium oxide thin films deposited by dual ion beam sputtering. X-ray diffraction (XRD), atom force microscopy (AFM), and Fourier transform infrared spectrum (FTIR) were employed to measure the crystalline structure, surface morphology, and infrared optical transmittance. The phase transition properties were characterized by transmittance. The results show that the annealed vanadium oxide thin film is composed of monoclinic VO2, with preferred orientation of (011). The maximum of transmittance change is beyond 65% as the temperature increases from 20 to 80°C. The reversible changes in optical transmittance against temperature were observed. The change rate of transmittance at short wavelength is higher than that at long wavelength at the same temperature across semiconductor-metal phase transition. This phenomenon was discussed using diffraction effect.

The influence of assisted ion beam bombardment on structure and electrical characteristics of HfSiO dielectric synthesized by DIBSD

We have investigated the influence of assisted ion beam bombardment on structure and electrical properties of HfSiO dielectrics deposited on Si (1 0 0) substrate by dual-ion beam sputtering deposition (DIBSD). The X-ray photoelectron spectroscopy (XPS) analysis indicates that assisted ion beam bombardment could suppress the formation of Si clusters and partial Si O bonds. The excellent electrical properties with maximum dielectric constant (18.6) and the smaller oxide-charge density (7.2 × 10 11 cm −2) and leakage current (2.8 × 10 −7 A/cm 2 at ( V fb−1) V) were obtained for HfSiO film by assisted ion beam bombardment at AIE = 100 eV, which provide a initial energy for the formation of film, activate the substrate surface atoms, enhance the polarization rate and improve the film surface compact and adhesion.

Influence of Ar+ Energy of Bombardment Cu Target and Low Energy Assisted Bombardment on Cu-W Thin Film Structure by Ion Beam Sputtering

This paper is to study the influence of Ar+ energy of bombardment Cu target and low energy assisted bombardment on Cu-W film structure in the preparation of Cu-W thin film by dual ion beam sputtering technique with iron as the substrate and argon as ion source. The results shown : when Ar+ energy of bombardment tungsten target is about 3keV, the beam of copper target is 20mA, Ar+ energy of bombardment Cu target is 1kev, 1.5kev and 2keV respectively, Cu-W thin film prepared by ion beam sputtering exists with the skeleton of tungsten in amorphous phase mixing with copper grains; with the increase of Ar+ energy of of bombardment copper target, the grain size of copper increases slightly; influenced by crystal defects and lattice distortion, copper diffraction peak offsets a little. Low energy assisted bombardment helps to increase grain growth of copper and can decrease crystal defects and lattice distortion. But with excessive energy, thin film fails to deposit.

Influence of Metal Electrode(Ag,Au,Pt) on the Dielectric and Electrical Properties of HfTaO Capacitors

HfTaO-based MOS capacitors with different top electrode (Ag、Au、Pt) were successfully fabricated by dual ion beam sputtering deposition (DIBSD). We presented the effect of different metal gate on the capacity, flat band voltage shift, leakage current and conduction mechanism. It has been found that the Pt-electrode capacitor exhibited the highest accumulation capacitance. In addition, the largest hysteresis loop in Pt/HfTaO/Si capacitor during the forward-and-reverse voltage sweeping from +2.5V to -2.5V was observed. The result indicates the presence of a large amount of fixed charges or oxygen vacancies exist in interface Pt/HfTaO, which is consistent with the prediction from Qf results. It is proved that even though Eot of the Pt-electrode capacitor is lower than that of the Ag, Au-electroded, and that of leakage current still has the smallest value at a high electric field due to Pt with a high enough work function Φms(Pt)=5.65eV.

Influence of assistant ion beam on the opto-electrical properties of molybdenum doped zinc oxide films deposited on polyethersulfone via dual ion beam sputtering

An alternative transparent conductive oxide, molybdenum doped zinc oxide (MZO) was deposited onto a flexible polyethersulfone (PES) substrate by using a dual ion beam sputtering system. One argon ion beam was used to sputter a MZO target and another assistant argon ion beam was for bombarding deposits simultaneously. The assistant ion source discharge voltage and current were changed respectively for investigating their influences on the conductivity of deposited MZO films. Changing the discharge voltage shows that, the film crystallinity, carrier concentration and mobility in films all increase with the discharge voltage and subsequently decrease when the applied voltage is over 100 V. Changing the discharge current also shows a similar trend. The film crystallinity and carrier concentration initially increase with the discharge current, and thereafter a minimum for 1.4 A, and a subsequent increase in resistivity is observed. According to the results, properly raising the discharge voltage and current of assistant ion source can improve both electrical conductivity and optical transparency of deposited MZO films, but the excess discharge voltage and current will cause the grain refinement which may retard the carrier mobility and result in the lower conductivity of MZO films.