Dual Ion Beam Sputtering Research Articles

Nanocrystalline magnetite thin films grown by dual ion-beam sputtering

We have explored the influence of an ion-assisted beam in the thermoelectric and magnetic properties of nanocrystalline magnetite thin films grown by ion-beam sputtering. The microstructure has been investigated by XRD. Tensile and compressive strained thin films have been obtained as a function of the parameters of the ion-assisted beam. The evolution of the in-plane magnetic anisotropy was attributed to crystalline grain size. In some films, magneto-optical Kerr effect measurements reveal the existence of uniaxial magnetic anisotropy induced by the deposition process related with a small grain size (⩽20nm). Isotropic magnetic properties have observed in nanocrystalline magnetite thin film having larger grain sizes. The largest power factor of all the films prepared (0.47μW/K2cm), obtained from a Seebeck coefficient of −80μV/K and an electrical resistivity of 13mΩcm, is obtained in a nanocrystalline magnetite thin film with an expanded out-of-plane lattice and with a grain size ≈30nm.

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.

Moisture absorption characteristics of a SiO2 film from 2 to 3 \mu m

We prepare SiO2 coatings on different substrates by either electron-beam evaporation or dual ion-beam sputtering. The relative transmittances of the SiO2 coatings are measured during the heating process. The SiO2 coating microstructures are studied. Results indicate that the intensity and peak position of moisture absorption are closely related to the microstructures of the coatings. The formation of microstructures depends not only on the preparation process of the coatings but also on the substrate characteristics.

高色散系数线性渐变滤光片的研制

On the basis of dual ion beam sputtering physical deposition method,a Linear Variable Filter(LVF)with a high transmittance and a high dispersion coefficient was fabricated by correction of linear gradual deposition rates.To get good quality,the linear varying trends of the two materials was matched to reduce their mismatch in film thickness correction processing.The spectral data of the LVF were obtained by the small spot method and the surface morphology and microstructure of the LVF were observed by a Scanning Electron Microscope(SEM).Tested results show that an alldielectric LVF with an operating range of 650-1 050 nm is obtained.In the range of 20 mm length,the center wavelength transmitted through LVF exhibits an excellent linear dependence(20nm/mm),and the linearity error is within 5nm along the direction of the wedge.The measured results indicate that the transmittance of the center wavelength is higher than 85%,and out-of-band transmittance isless than 0.1%.The LVF has good spectral characteristics and stability,thus can satisfy the system requirements for miniaturization,integration and stabilization.

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.

Improving the laser damage resistance of oxide thin films and multilayers via tailoring ion beam sputtering parameters

Ion beam sputtering is one of the widely used methods for manufacturing laser optical components due to its advantages such as uniformity, reproducibility, suitability for multilayer coatings and growth of dielectric materials with high packing densities. In this study, single Ta2O5 layers and Ta2O5/SiO2 heterostructures were deposited on optical quality glass substrates by dual ion beam sputtering. We focused on the effect of deposition conditions like substrate cleaning, assistance by 12cm diameter ion beam source and oxygen partial pressure on the laser-induced damage threshold of Ta2O5 single layers. Afterwards, the obtained information is employed to a sample design and produces a Ta2O5/SiO2 multilayer structure demonstrating low laser-induced damage without a post treatment procedure.

Influence of ion/atom arrival ratio on structure and optical properties of AlN films by ion beam assisted deposition

In order to improve the optical properties of AlN films, the influence of the ion/atom arrival ratio on the structure and optical characteristics of AlN films deposited by dual ion beam sputtering was studied by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry and UV–vis spectroscopy. The films prepared at the ion/atom arrival ratio of 1.4 are amorphous while the crystalline quality is improved with the increase of the ion/atom arrival ratio. The films deposited at the ion/atom arrival ratio of no less than 1.8 have an approximately stoichiometric ratio and mainly consist of aluminum nitride with little aluminum oxynitride, while metallic aluminum component appears in the films deposited at the ion/atom arrival ratio of 1.4. When the ion/atom arrival ratio is not less than 1.8, films are smooth, high transmitting and dense. The films prepared with high ion/atom arrival ratio (≥1.8) display the characteristic of a dielectric. The films deposited at the ion/atom arrival ratio of 1.4 are coarse, opaque and show characteristic of cermet.

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.

Nanosecond laser-induced damage at different initial temperatures of Ta2O5 films prepared by dual ion beam sputtering

Ta2O5 films were deposited by dual ion beam sputtering method. The nanosecond laser-induced damage threshold (LIDT) at different initial temperatures and time of the films was investigated by an in situ high temperature laser-induced damage testing platform. It was shown that, when the initial temperature increased from 298 K to 383 K, the LIDT at 1064 nm and 12 ns significantly decreased by nearly 14%. Then the LIDT at 1064 nm and 12 ns decreased slower with the same temperature increment. Different damage morphologies were found at different initial temperatures. At low initial temperatures, it was the defects-isolated damage while at high initial temperatures it was the defects-combined damage. The theoretical calculations based on the defect-induced damage model revealed that both the significant increase of the highest temperature and the duration contributed to the different damage morphologies. With the initial temperature being increased, the thermal-stress coupling damage mechanism transformed gradually to the thermal dominant damage mechanism.

Influence of ion-beam sputtering deposition parameters on highly photosensitive and transparent CdZnO thin films

CdZnO thin films with a nominal thickness of ~200 nm were grown on c-plane sapphire substrates by dual ion-beam sputtering deposition technique. The effect of substrate temperature (300–600 °C) and gas ambience on structural, morphological, compositional and opto-electronic properties was studied. X-ray diffraction patterns confirmed that all the films were polycrystalline in nature and were preferentially oriented along the c-axis. It was revealed that the films grown at Ar/O2 ratio of 4:1 were structurally more ordered and the film quality was found to be the best at 500 °C. The compositional studies specify that approximately 11.8 at.% of cadmium were present in the film deposited at 300 °C in Ar–O2 mixture. Investigations on optical properties by photoluminescence and absorption studies indicate band gap shrinkage with the increase in argon partial pressure and substrate temperature. It was found that photosensitivity of the deposited films was highly dependent on growth conditions. The photosensitivity was found to be 5000-fold higher for CdZnO film grown at 600 °C in Ar–O2 ambience compared to the best reported result, and this was promising to realize high-performance opto-electronic devices on such CdZnO films.

Growth and characterizations of dual ion beam sputtered CIGS thin films for photovoltaic applications

The growth of CIGS thin films on soda-lime glass substrates at different substrate temperatures by dual ion beam sputtering system in a single-step route from a single quaternary sputtering target with the composition of Cu (In0.70 Ga0.30) Se2 was reported. The effects of the substrate temperature on structural, optical, morphological and electrical properties of CIGS films were investigated. Stoichiometry of one such film was investigated by X-ray photoelectron spectroscopy. All CIGS films had demonstrated a strong (112) orientation located at 2θ ~26.70o, which indicated the chalcopyrite structure of films. The value of full-width at half-maximum of (112) peak was reduced from 0.58° to 0.19° and crystallite size was enlarged from 14.98 to 43.05 nm as growth temperature was increased from 100 to 400 °C. However, atomic force microscope results showed a smooth and uniform surface at lower growth temperature and the surface roughness was observed to increase with increasing growth temperature. Hall measurements exhibited the minimum film resistivity of 0.09 Ω cm with a hole concentration of 2.42 × 1018 cm−3 and mobility of 28.60 cm2 V−1 s−1 for CIGS film grown at 100 °C. Film absorption coefficient was found to enhance nominally from 1 × 105 to 2.3 × 105 cm−1 with increasing growth temperature from 100 to 400 °C.

Inelastic tunneling conductance and magnetoresistance investigations in dual ion-beam sputtered CoFeB(110)/MgO/CoFeB (110) magnetic tunnel junctions

Magnetic tunnel junctions (MTJs) comprising Ta(5)/NiFe(5)/IrMn(15)/CoFeB(5)/Mg(1)/MgO(3.5)/ CoFeB(5)/Ta(5)/Ag(20) (thickness in nm) with (110) oriented CoFeB layers are grown using dual ion beam sputtering. The tunnel magnetoresistance (TMR) of MTJs is found to be significantly bias dependent and exhibits zero bias anomaly (ZBA) which is attributed to the presence of magnetic impurities or diffusion of Mn from antiferromagnetic IrMn in the barrier. Adjacent to the ZBA, two peaks at 24 ± 3 mV and 34 ± 3 mV are also observed, which differ both in intensity as well as their position in the antiparallel and parallel magnetic states, suggesting that they are due to magnon excitations. In addition to this, a phonon peak at 65 ± 3 mV is also observed. The effect of temperature on the inelastic and elastic tunneling contributions is studied in detail in 25–300 K range using the Glazman and Matveev model. Ten series of localized states are found to be involved in hopping conduction in the forbidden gap of MgO barrier. The effect of presence of such inelastic channels is found to be insignificant at low temperatures yielding sizeable enhancement in TMR.

Study and Fabrication of Filter Film in Tactical Optical Fiber Communication System

The development of optical fiber transmission technology provides a broad application prospect for the communication of real-time battlefield information. The information could be communicated between the front and headquarters through the cable by using tactical optical fiber communication system, which ensures the missions of military intelligence communicated and tactical real-time arrangement are completed successfully. According to the requirements of multiplexer for military tactical optical fiber communication system, the filters with low-loss have been developed. Filters are prepared by the depositing method of dual ion beam sputtering, Nb2O5 and SiO2 have been chosen as deposition materials, and the filter film is designed and optimized with the help of TFCalc software. In order to broaden the shortwave cutoff region of the filter, the long-wave pass film have been added behind the initial film, and the thickness of the matching layers have been optimized, which based on the concept of equivalent refractive index, the insertion loss of the pass-band of the filter has been reduced. The optical extreme value method and average time method have been used to control layers thickness, and the problem of the layers thickness accuracy controlling have been solved by using the method of real-time calibration of the deposition rate and the repeatability of parameters accurately control. The transmission spectrum of the filter has been tested, which demonstration that the center wavelength of the filter is 1511.2nm, the width of the filters pass band is 17.1nm and 23.5nm in the region of-0.5dB and-35dB respectively, the worst insertion loss within pass band region is-0.1dB, the ripple of the pass band is 0.06dB. The results show that the preparation of the filter meets the using requirements of military tactical fiber optic communication system well.

Evaluation of magnetic flux distribution from magnetic domains in [Co/Pd] nanowires by magnetic domain scope method using contact-scanning of tunneling magnetoresistive sensor

Current-driven magnetic domain wall motions in magnetic nanowires have attracted great interests for physical studies and engineering applications. The magnetic force microscope (MFM) is widely used for indirect verification of domain locations in nanowires, where relative magnetic force between the local domains and the MFM probe is used for detection. However, there is an occasional problem that the magnetic moments of MFM probe influenced and/or rotated the magnetic states in the low-moment nanowires. To solve this issue, the “magnetic domain scope for wide area with nano-order resolution (nano-MDS)” method has been proposed recently that could detect the magnetic flux distribution from the specimen directly by scanning of tunneling magnetoresistive field sensor. In this study, magnetic domain structure in nanowires was investigated by both MFM and nano-MDS, and the leakage magnetic flux density from the nanowires was measured quantitatively by nano-MDS. Specimen nanowires consisted from [Co (0.3)/Pd (1.2)]21/Ru(3) films (units in nm) with perpendicular magnetic anisotropy were fabricated onto Si substrates by dual ion beam sputtering and e-beam lithography. The length and the width of the fabricated nanowires are 20 μm and 150 nm. We have succeeded to obtain not only the remanent domain images with the detection of up and down magnetizations as similar as those by MFM but also magnetic flux density distribution from nanowires directly by nano-MDS. The obtained value of maximum leakage magnetic flux by nano-MDS is in good agreement with that of coercivity by magneto-optical Kerr effect microscopy. By changing the protective diamond-like-carbon film thickness on tunneling magnetoresistive sensor, the three-dimensional spatial distribution of leakage magnetic flux could be evaluated.

Indium Tin Oxide Thin Films Deposited at Low Temperature Using Dual Ion Beam Sputtering

ABSTRACTITO samples were sputtered at room temperature by ion assisted dual ion beam sputtering using atomic or molecular oxygen. The electrical properties appear to depend on the oxygen flow rate during deposition and the resistivity decreases for samples sputtered at a higher oxygen flow rate (1-5 sccm). The resistivity is lowest at an oxygen flow rate of 4 sccm. The average absorption in the visible part of the spectrum also decreases as a function of the oxygen flow rate and is lower for samples sputtered with atomic oxygen. The figure of merit, i.e. the ratio of the conductivity versus the average absorption in the visible range, increases for higher oxygen flow rates and is typically 20-60% higher for samples sputtered using an atomic oxygen assist beam.

Electrical and Optical Properties of Permalloy Oxide grown by dual ion beam sputtering.

ABSTRACTElectrical and Optical measurements were carried out on permalloy oxide (PyO) thin films made by reactive dual ion beam sputtering at room temperature. VSM measurements at room temperature and 15 Kelvin did not reveal any magnetic moment in 120 nm thick films. The optical refraction and extinction spectra from 200-1000 nm were determined from ellipsometry measurements using a Cody-Lorentz model and provided in a reproducible method to determine the film thickness of PyO films on different substrate materials. PyO is transparent above 700 nm and is strongly absorbing below 500 nm. The resistivity values of PyO samples sputtered at room temperature depend on the oxygen flow rate and is approximately 4E3 Ohm cm for films prepared at 10 sccm. The resistivity of PyO decreases as a function of temperature. The dielectric constant is strongly frequency dependent, decreasing from 500 at 500 Hz to 10 at 1 MHz.

Behavior of dual ion beam sputtered MgZnO thin films for different oxygen partial pressure

Mg-doped ZnO (MgZnO) films were grown on p-Si (001) substrates by dual ion beam sputtering deposition system at a constant growth temperature of 600 °C for different oxygen partial pressure. The impact of oxygen partial pressure on the structural, electrical, elemental and morphological properties was thoroughly investigated. X-ray diffraction (XRD) spectra revealed that the deposited MgZnO films were polycrystalline in nature with preferred (002) crystal orientation. The peak of MgZnO (101) plane was reduced significantly as oxygen partial pressure was increased and disappeared completely at 80 and 100 % O2. The maximum electron concentration was evaluated to be 5.79 × 1018 cm−3 with resistivity of 0.116 Ω cm and electron mobility of 9.306 cm2/V s at room temperature, for MgZnO film grown with 20 % O2. Raman spectra shows a broad peak at 434 cm−1 corresponded to E 2 high phonons mode of MgZnO wurtzite structure. The peak at 560 cm−1 corresponded to the E1 (LO) mode and was associated with oxygen deficiency in MgZnO films. Raman intensity at 560 cm−1 reduced, on increasing oxygen partial pressure. A correlation between structural, electrical, elemental and morphological properties with oxygen partial pressure was also established.

Interface characteristics of peeling-off damages of laser coatings

Coating stacks of HfO2/SiO2 and Ta2O5/SiO2 were separately prepared by electron beam evaporation and dual ion beam sputtering. Damage characteristics at the interlayer interfaces were analyzed after irradiation of the coatings by a 1064nm laser. The cross-sectional morphologies of damage spots indicated that peeling-off damages always occurred at the interface where the low refractive index material (SiO2) was deposited on the high refractive index material (HfO2 or Ta2O5). The effects of interface microstructure and components on peeling-off damages were also discussed. The microstructure of the interface was not a major factor that influenced peeling-off damages. Incomplete oxides (SiOx) and Na, K, Li ions accumulated near the interface and caused the formation of micro-defects layers with nano-sized thicknesses. Micro-defects layers maybe reduced adhesion of different interfaces and formed plasmas by absorbing laser energy. Finally stripping damages happened from micro-defects layers during irradiation by a 1064nm laser.

P-type conduction from Sb-doped ZnO thin films grown by dual ion beam sputtering in the absence of oxygen ambient

Sb-doped ZnO (SZO) thin films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system in the absence of oxygen ambient. The electrical, structural, morphological, and elemental properties of SZO thin films were studied for films grown at different substrate temperatures ranging from 200 °C to 600 °C and then annealed in situ at 800 °C under vacuum (pressure ∼5 × 10−8 mbar). Films grown for temperature range of 200–500 °C showed p-type conduction with hole concentration of 1.374 × 1016 to 5.538 × 1016 cm−3, resistivity of 66.733–12.758 Ω cm, and carrier mobility of 4.964–8.846 cm2 V−1 s−1 at room temperature. However, the film grown at 600 °C showed n-type behavior. Additionally, current-voltage (I–V) characteristic of p-ZnO/n-Si heterojunction showed a diode-like behavior, and that further confirmed the p-type conduction in ZnO by Sb doping. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. X-ray photoelectron spectroscopy analysis confirmed the formation of SbZn–2VZn complex caused acceptor-like behavior in SZO films.

Investigation of dual ion beam sputtered transparent conductive Ga-doped ZnO films

Ga-doped ZnO (GZO) transparent conducting films were deposited on sapphire (0001) substrates using dual ion beam sputtering deposition system. The impact of growth temperature on the structural, morphological, elemental, optical, and electrical properties was thoroughly investigated and reported. X-ray diffraction measurements explicitly confirmed that all GZO films had (002) preferred crystal orientation. The film deposited at 400 °C exhibited the narrowest full-width at half-maximum value of 0.24° for (002) crystalline plane and the lowest room temperature electrical resistivity of 4.11 × 10−3 Ω cm. The Raman spectra demonstrated the vibrational modes at 576 and 650–670 cm−1, associated with native oxygen vacancies and elemental Ga doping in ZnO lattice, respectively. All doped films showed an overall transmittance of above 95 % in the visible spectra. A correlation between structural, optical, elemental, and electrical properties with GZO growth temperature was established.