Secondary Ion Mass Spectrometry Depth Profiling Research Articles

Quantification of secondary ion mass spectrometry measurements by using ion‐implanted metallic standards

This research addresses an analytical methodology to quantify elements of interest in fusion‐relevant materials using secondary ion mass spectrometry (SIMS). For this purpose, internal standards have been fabricated by ion implantation to avoid the well‐known matrix effect of this technique. In particular, chromium has been implanted at an energy of 12 MeV using two fluences in high‐purity iron and tungsten matrices together with Si control substrates. The latter were applied to determine the Cr concentration implanted through experimental and semiempirical methods. Specifically, the IBA technique Rutherford backscattering spectrometry (RBS) provided the quantitative results being 3.1 × 1019 at/cm3 and 1.6 × 1019 at/cm3 for the high and low dose, respectively. The SIMS depth profiles of Cr for the Fe and W matrices established an ion implantation depth close to 2 μm on both substrates in agreement with the calculations previously performed by Stopping and Range of Ions in Matter (SRIM) simulations. Correlation between the integration of SIMS profiles and known concentrations of the implanted ion resulted in the calibration curve for each matrix, obtaining the SIMS quantification approach by means of this relative sensitivity factor (RSF). Additionally, a cross‐check of the method by comparing commercial Fe‐Cr alloys with the Cr‐implanted Fe matrices of the present study pointed out the need to produce standards with higher chromium concentrations.

The Effect of Sodium on a Molybdenum Layer by Varying the Growth Pressure on CIGS Solar Absorp-tion Layer

Flexible Cu (In, Ga) Se2 (CIGS) solar cells on stainless-steel (STS) substrates face the problem of efficiency deterioration when iron impurities diffuse into the absorber layer. Iron, the main component of stainless steel, can diffuse through the back contact into the CIGS absorber, where Fe impurities are known to reduce the solar cell performance. In this work, the sodium-doped Molybdenum (Mo-Na) layer was made as a diffusion barrier on STS substrate for various growth pressures. The formed Mo-Na diffusion barrier layer was analyzed by Scanning Electron Microscopy, X-ray diffractometer and UV-Vis Spectrophotometer. X-ray diffraction showed that the films grown on STS substrates had a pure chalcopyrite phase with a preferred (112) orientation Mo back contact and the CIGS layer was subsequently deposited by co-sputtering technique and selenization process, to investigate the Na diffusion through the diffusion barrier into the CIGS absorption layer. The concentrations of Na and Fe diffused in the CIGS layer were also measured by secondary ion mass spectroscopy (SIMS). The SIMS depth profile and optical measurement results demonstrated that the diffusion of Na into the CIGS absorber layer was controlled by varying the working pressure of the Mo-Na layer.

Secondary Ion Mass Spectrometry Study of Hydrogenated Amorphous Silicon Layer Disintegration upon Rapid (Laser) Annealing

Double layers of deuterated and hydrogenated amorphous silicon (a‐Si:H) on glass are heated in the ambient by scanning with a green (532 nm) continuous wave laser. The hydrogen diffusion length in the laser spot is obtained from the deuterium (D)–hydrogen (H) interdiffusion measured by secondary ion mass spectrometry (SIMS), the temperature in the laser spot is obtained by calculation. Under certain conditions, detachment of the deuterated layer from the hydrogenated layer is observed in the SIMS depth profiles, visible by rising oxygen and carbon signals at the D/H interface attributed to in‐diffusion of atmospheric gas species like water vapor, oxygen, and carbon oxide. Stacks involving both undoped and boron‐doped a‐Si:H films show disintegration. The results suggest that the parameters leading to the disintegration effects are the presence of a plane of reduced material cohesion at the D/H interface, a sizeable H diffusion length and a rather high heating rate. Herein, it is likely considered that the observed layer disintegration process is involved in the peeling of a‐Si:H films upon fast heating. Furthermore, the results show that rapid laser heating can be used to detect planes of reduced material cohesion which may compromise the electronic properties of a‐Si:H‐based stacks.

Depth distribution analysis of alloying and impurity elements in Ni-Ti alloy thin films using secondary ion mass spectrometer

Ni-rich Ni-Ti thin films of various compositions and thickness (69 nm - 141 nm) were deposited on Si (111) substrate by magnetron sputtering system using equiatomic NiTi alloy sputtering target. X-ray reflectivity analysis of the thin films deposited at room temperature showed the presence of a layered structure as: NiO/Ni-Ti/NiO/SiO2 on Si substrate. Secondary ion mass spectrometry (SIMS) was used to determine the qualitative (intensity) depth distribution of elements Ni, Ti, O and Si in the films using MCs+ approach. Relative sensitivity factor values were utilized to convert the qualitative depth profiles to concentration depth profiles. Surface and depth distribution of alloying elements in the deposited films were investigated. It was observed that the films deposited at high sputtering power and working pressure resulted in more non-uniform depth distribution of alloying elements compared to films deposited at low sputtering power and working pressure. SIMS depth profile data showed the presence of high oxygen contaminations at the surface and at the interface of the films. The Ti concentration in the deposited films depends upon the background oxygen contamination present in the deposition chamber during sputtering process. The concentration of Ni in the films deposited under similar working pressure increases with increase in the sputtering power. However, with increase in working pressure during deposition process results in decrease in the concentration of both Ni and Ti in the deposited films. In order to study the effect of insitu substrate heating on the distribution of alloying and impurity elements, one of the film was deposited on heated Si substrate. The film deposited on heated substrate represents the layer structure as NiTiO3 on Si substrate. The concentration of oxygen in the film deposited on heated substrate is comparatively higher than those deposited at room temperature.

Determination of relative sensitivity factor, sputtering rate, and detection limits of deuterium in deuterium ion‐implanted Zircaloy‐4 using secondary ion mass spectrometer

Zirconium‐based alloys are extensively used in the nuclear industry as materials for reactor core components. These alloys are used in fuel cladding and pressure tubes with 1H2O or 2H2O as the primary heat exchange fluid. Continuous usage of pressure tubes and fuel cladding inside the reactor results in heavy ingress of hydrogen (1H) or deuterium (2H), which gives rise to the formation of hydrogen (or deuterium) precipitates in the host of zirconium matrix. This is called hydrogen (or deuterium) embrittlement phenomenon. Therefore, determination of hydrogen or deuterium concentration periodically in zirconium alloy pressure tubes and cladding are crucial for safe operation of nuclear reactors. Hence, in this work, secondary ion mass spectrometry (SIMS) has been utilized to determine the relative sensitive factor (RSF), sputtering rate, and detection limits of 2H in 2H+ ion‐implanted Zircaloy‐4 sample. SIMS analysis has been carried out using O2+ and Cs+ primary ion beams. Depth profiles of various elemental and molecular secondary ions have been monitored to determine the RSF values and detection limits of 2H in the sample under different primary ion beam analysis conditions. Sputtering rate under different analysis conditions has also been determined from the correlation between the projected range of 2H+ ions in Zircaloy‐4 sample determined from Stopping and Range of Ions in Matter (SRIM) software and the depth of the crater formed by primary ion beam bombardment process. The projected range of 2H+ ions in Zircaloy‐4 was estimated to be ~524.2 nm using the simulation carried out by SRIM software. The projected range, evaluated by SRIM software, was utilized for depth scale calibration of SIMS sputtered time profiles. The SIMS depth profiles were also calibrated by determining the depth of the SIMS crater by using optical depth profilometer. The values of range estimated by SRIM as well as optical profilometer were found to be in good agreement, within instrument uncertainty.

SIMS Analysis of Thin EUV Photoresist Films.

This study reports on the application of secondary ion mass spectrometry (SIMS) for examining thin (20-50 nm) chemically amplified resist films on silicon. SIMS depth profiling was carried out using a gas cluster ion beam to ensure minimal sputter-induced damage to the organic constituents of interest. Specific attention concerned the distribution of the photo acid generator (PAG) molecule within these films, along with the photo-induced fragmentation occurring on extreme ultra-violet photo exposure. Positive secondary ion spectra were collected using a traditional time of flight (ToF)-SIMS and the latest generation IONTOF Hybrid SIMS instrumentation equipped with an OrbitrapTM mass analyzer. Tandem mass spectrometry (MS/MS) capability within the OrbitrapTM secondary ion column was utilized to verify that the C19H17S+ secondary ion did indeed have the molecular structure consistent with the PAG structure. The superior mass resolving power of the OrbitrapTM mass analyzer (∼20× of the ToF mass analyzer) along with improved mass accuracy (a few ppm) proved pivotal in the mass spectral and depth profile analysis of these films. This was not the case for the ToF-SIMS experiments, as the mass spectra, as well as the associated depth profiles, exhibited severe molecular (isobaric) interferences.

Stabilizing effects of Ag doping on structure and thermal stability of FeN thin films

In this work, we investigated the effect of Ag doping (2–20 at.%) on the phase formation of iron mononitride (FeN) thin films. Together with deposition of FeN using reactive dc magnetron sputtering, Ag was also co-sputtered at various doping levels between 2–20 at.%. We found that doping of Ag around 5 at.% is optimum to not only improve the thermal stability of FeN but also to reduce intrinsic defects that are invariably present in (even in epitaxial) FeN. Conversion electron Mössbauer spectroscopy and N K-edge x-ray near edge absorption measurements clearly reveal a reduction of defects in Ag doped FeN samples. Moreover, Fe self-diffusion measurements carried out using secondary ion mass spectroscopy depth-profiling and polarized neutron reflectivity in 57Fe enriched samples exhibit an appreciable reduction in Fe self-diffusion in Ag doped FeN samples. Ag being immiscible with Fe and non-reactive with N, occupies grain-boundary positions as nanoparticles and prohibits the fast Fe self-diffusion in FeN.

Argon cluster‐ion sputter yield: Molecular dynamics simulations on silicon and equation for estimating total sputter yield

Argon Gas Cluster‐Ion Beam sources have become widely‐used on X‐ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) instruments in recent years, but there is little reference data on sputter yields in the literature as yet. Total sputter yield reference data is needed in order to calibrate the depth scale, of XPS or SIMS depth profiles. We previously published a semi‐empirical ‘Threshold’ equation for estimating cluster total sputter yield from the energy‐per‐atom of the cluster and the effective monatomic sputter threshold of the material. This has been shown to agree extremely well with sputter yield measurements on a range or organic and inorganic materials for clusters of around a thousand atoms. Here we use the molecular dynamics (MD) approach to explore a wider range of energy and cluster size than is easy to do experimentally to high precision. We performed MD simulations using the ‘Large‐scale Atomic/Molecular Massively Parallel Simulator’ (LAMMPS) parallel MD code on high‐performance computer (HPC) systems. We performed 1150 simulations of individual collisions with a silicon (100) surface as an archetypal inorganic substrate, for cluster sizes between 30 and 3000 argon atoms and energies in the range 5 to 40 eV per atom. This corresponds to the most important regime for experimental cluster depth‐profiling in SIMS and XPS. Our MD results show a dependence on cluster size as well as energy‐per‐atom. Using the exponent previously suggested by Paruch et al., we modified the Threshold model equation published previously to take this into account. The modified Threshold equation fits all our MD results extremely well, building on its success in fitting experimental sputter yield measurements.This work is submitted to the volume dedicated to Dr. Martin P Seah, MBE, who was a great influence on the early career of one of the authors (PJC) and who himself made many valuable contributions to the literature on sputtering as it relates to surface and interface analysis.

N-Type doping of ε-Ga2O3 epilayers by high-temperature tin diffusion

The good control of the n-type doping is a key issue for the fabrication of efficient devices based on ε-Ga2O3 epilayers. In this work we studied the possibility of doping the ε-Ga2O3 thin films, epitaxially grown on c-oriented sapphire by metal-organic chemical vapor deposition, by means of a post-deposition treatment. For the first time, the n-type doping was achieved by depositing a tin-rich SnO2 film on top of the ε-Ga2O3 layer and keeping this bi-layer system for 4 h at a temperature of 600 °C in an evacuated furnace. The diffusion of Sn atoms into the ε-Ga2O3 film is evidenced by time-of-flight secondary-ion mass spectrometry depth profiles. Room-temperature resistivity of the order of 1 Ω•cm is obtained and the electrical characterization revealed a conduction mechanism based on variable range hopping, according to the Mott's model.

N-Type Doping of ε-Ga <sub>2</sub>O <sub>3</sub>n Epilayers by High-Temperature Tin Diffusion

The good control of the n-type doping is a key issue for the fabrication of efficient devices based on e-Ga2O3 epilayers. In this work we studied the possibility of doping the e-Ga2O3 thin films, epitaxially grown on c-oriented sapphire by metal-organic chemical vapor deposition, by means of a post-deposition treatment. For the first time, the n-type doping was achieved by depositing a tin-rich SnO2 film on top of the e-Ga2O3 layer and keeping this bi-layer system for 4 hours at a temperature of 600 °C in an evacuated furnace. The diffusion of Sn atoms into thee-Ga2O3 film is evidenced by time-of-flight secondary-ion mass spectrometry depth profiles. Room-temperature resistivity of the order of 1 Ω cm is obtained and the electrical characterization revealed a conduction mechanism based on variable range hopping, according to the Mott’s model.

MD-Based Transport and Reaction Model for the Simulation of SIMS Depth Profiles of Molecular Targets

We present a novel theoretical approach allowing us to model erosion and chemical alteration of organic samples during depth profiling analysis by secondary-ion mass spectrometry with cluster projectile ion beams. This approach is able to take into account all of the cumulative phenomena occurring during such analysis, including ion-beam-induced reactions and atomic/molecular mixing by means of the numerical solution of an advection–diffusion–reaction (ADR) differential equation. The results from the single-impact molecular dynamics computer simulations are used as a source for the input parameters into the ADR model. Such an approach is fast and allows turning the phenomenological model into a more quantitative tool capable of calculating molecular secondary-ion mass spectrometry depth profiles. The model is used to describe phenomena taking place during depth profiling of polystyrene samples by 20 keV C60, Ar872, and Ar1000 projectiles. It is shown that theoretical findings are in good agreement with th...

Characterization studies of NiO:K anode buffer layer in Alq3 and TADF-based organic light-emitting diodes by secondary ion mass spectrometry and admittance spectroscopy

In this paper, we used thermal evaporation method to deposit metal oxide films as inorganic buffer layer in Organic light-emitting diodes (OLEDs), and investigated how the K2CO3-doped NiO (KNO) buffer layers affect OLEDs’ performances. The mechanisms of enhanced hole injection into the hole transport layer NPB (α-naphthylphenylbiphenyl diamine) via NiO:K2CO3 anode buffer layers in Alq3-based and TADF-based OLEDs were studied by means of J-V-L characteristics, secondary ion mass spectroscopy (SIMS), and admittance spectroscopy measurements. For Alq3-based OLEDs, devices’ opto-electrical performances showed increased of luminance from 8780 cd/m2 to 22940 cd/m2, the decreased of turn-on voltage from 3.4 V to 3.1 V at 1 mA/cm2, and increased of current efficiency from 4.3 cd/A to 3.48 cd/A when 1-nm-thick K2CO3-doped NiO film with doping concentration of 1 mol% was inserted into OLEDs. TADF-based OLEDs’ current efficiency increased from 21.7 cd/A to 29.7 cd/A with similar anode buffer layer parameters. SIMS depth profiles on OLEDs suggested higher indium (In) diffusion from ITO anode onto TADF-based OLEDs upon device operation leading to higher roll-off phenomenon. Deposition of NiO:K2CO3 as anode buffer layer onto OLEDs device reduced the diffusion of In in organic layers during device operation. Investigation of the capacitance as function of voltage and frequency yield information about carrier injection characteristics for both Alq3 and TADF-based OLEDs. Due to better carrier recombination capability, TADF-based OLEDs’ slope in V > Vbi area has fewer shifts and more stable response, leading to higher amplitude in current efficiency enhancement in comparison with fluorescents (Alq3) material.

Atomic Layer Deposition of Titania in Ordered Mesoporous Cerium Zirconium Oxide Thin Films: A Case Study

A strategy is presented to deposit defined layers of TiO2 onto the pore surface within ordered mesoporous, crystalline CeO2-ZrO2 thin films using atomic layer deposition (ALD). As structure-directing agent, a special diblock copolymer, poly(isobutylene)-block-poly(ethylene oxide), was used, resulting in a three-dimensional arrangement of spherical pores with diameter around 13 nm. High resolution transmission electron microscopy investigations evidence the presence of anatase TiO2 coatings within the mesopores, while ellipsometric porosimetry studies together with time-of-flight secondary-ion mass spectrometry depth profiles indicate the deposition inside the mesopores up to 50 ALD cycles. Afterward, the interconnecting channels between the mesopores are filled completely prohibiting further transport of the gaseous TiO2 precursor into the ordered structure of mesopores and hence, limit the layer growth on the surfaces of the pores. Therefore, the size of the mesopores and their connections are decisive w...

Iterative deconvolution using the MRI model for removing experimental broadening and shift effects in SIMS depth profiles

During the last years, depth resolution of secondary ion mass spectrometry (SIMS) has been enhanced, mainly by solving direct and inverse problems of depth profiling. The solution of both problems is based on the depth resolution function (DRF). Solving the direct problem is frequently done by using the DRF of the Mixing‐Roughness‐Information depth (MRI) model, and solving the inverse problem is frequently achieved by using the DRF proposed by Dowsett and coworkers. However, using the latter may create difficulties in determining the true position of the measured profiles. In this paper, it is proposed to solve iteratively the inverse problem of SIMS depth profiling using the analytical DRF of the MRI model. The iterative deconvolution using the MRI model is tested on theoretical and experimental profiles. It is shown that the proposed procedure is able to provide a non‐negligible improvement; the artificial broadening of the measured profiles is clearly reduced, and their shift from the actual positions is corrected.

Application of ‘Storing Matter’ technique in SIMS depth profile analysis

Secondary ion mass spectrometry (SIMS) is a very useful technique for the analysis of layered systems. It is based on the primary ion beam sputtering of solids and mass analysis of the emitted secondary ions. A main limitation of this technique results from the direct quantitative analysis, since the ionization efficiency of a given atom is highly influenced by the neighbouring atoms at the surface. This phenomenon is known as the ‘matrix effect’.This problem can be partially solved by separation of the sputtering and ionization processes. The ‘Storing Matter’ technique involves deposition of the sputtered matter onto a rotating collector. Subsequently, ionisation occurs during the ion beam bombardment of the stored matter.In case of sputtering of a given layered structure, the stored matter deposit presents the sequence of the deposition process and the analysis of this deposit reflects the investigated structure.We analyse a set of on oxidized steel samples and oxidized steel covered by aluminium. These types of structures are known for strong matrix effects at the metal oxide interfaces. The results of the ‘Storing Mater’ analyses are compared with the results of the classical SIMS analysis.

Non-destructive determination of ultra-thin GaN cap layer thickness in AlGaN/GaN HEMT structure by angle resolved x-ray photoelectron spectroscopy (ARXPS)

Angle resolved X-ray photoelectron spectroscopy (ARXPS) and secondary ion mass spectrometry (SIMS) investigations have been carried out to characterize the GaN cap layer in AlGaN/GaN HEMT structure. The paper discusses the qualitative (presence or absence of a cap layer) and quantitative (cap layer thickness) characterization of cap layer in HEMT structure non-destructively using ARXPS measurements in conjunction with the theoretical modeling. Further the relative sensitive factor (RSF=σGaσAl) for Ga to Al ratio was estimated to be 0.963 and was used in the quantification of GaN cap layer thickness. Our results show that Al/Ga intensity ratio varies with the emission angle in the presence of GaN cap layer and otherwise remains constant. Also, the modeling of this intensity ratio gives its thickness. The finding of ARXPS was also substantiated by SIMS depth profiling studies.

Critical need and future directions of SIMS depth profiling in CMOS fabrication

The complementary metal-oxide-semiconductor (CMOS) industry continues to push the boundaries of what is possible. Along with this, secondary ion mass spectrometry (SIMS) depth profiling continues to support CMOS R&D and high volume manufacturing (due to its unparalleled sensitivity and detection limits over predefined volumes and within acceptable time periods). New developments in SIMS are also being realized to support the move of the CMOS industry from planar structures to three-dimensional (3D) structures. This article presents a perspective of existing SIMS research areas for beyond one-dimensional structural analysis along with potential future SIMS implementation and data processing scenarios. The topics covered include: (1) existing SIMS depth profiling approaches for 3D structures, (2) in-fab SIMS deployment, (3) data analysis of in-fab SIMS derived depth profiles from 3D structures via pattern recognition, and (4) hybrid characterization approaches. With SIMS depth profiling of optimized (for SIMS) 3D structures already demonstrated, the remaining topics may serve to extend these and other capabilities and open new application areas for SIMS.

Determination of the oxide scale growth mechanism using 18O-tracer experiments in combination with Transmission Electron Microscopy and nanoscale Secondary Ion Mass Spectrometry

Two-stage 18O2/16O2 exposures can be used to investigate the effect that alloying elements, secondary phases, or surface treatments have on the high temperature oxidation behaviour of certain materials. During subsequent exposures to 16O2- and 18O2-rich atmospheres, 16O- and 18O-rich layers are formed. Analysis of the layers using Secondary Ion Mass Spectrometry (SIMS) depth profiling allows for conclusions to be drawn about the oxide scale growth mechanism. The conclusions are, however, not entirely unambiguous due to the limited lateral resolution of the technology. Rough surface topography and the thickness variation of the oxide scale over the analysed volume add to the ambiguity of the findings. In this study, an Fe-20%Cr alloy was exposed to both 18O- and 16O-rich environments at 850°C. Two methods were used to analyse the thermally grown Cr2O3 scale: (1) traditional SIMS depth profiling and (2) preparation of a cross-sectional lamellae for Transmission Electron Microscopy (TEM), which, subsequently, was analysed in a NanoSIMS. The NanoSIMS 16O and 18O elemental maps were then superimposed on the TEM image. In comparison with traditional SIMS depth profiling, the nanoSIMS elemental maps reveal detailed information about local oxide growth in different parts of an oxide scale. Moreover, a clear 16O/18O interface can be seen in the nanoSIMS maps, which is not the case in the sputter depth profiles. The findings of this study show that the aforementioned issues associated with sputter depth profiling can be eliminated by mapping a cross-section of an oxide scale using high resolution nanoSIMS.

Quantitative analysis of Si1-xGex alloy films by SIMS and XPS depth profiling using a reference material

Quantitative analysis methods of multi-element alloy films were compared. The atomic fractions of Si1-xGex alloy films were measured by depth profiling analysis with secondary ion mass spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS). Intensity-to-composition conversion factor (ICF) was used as a mean to convert the intensities to compositions instead of the relative sensitivity factors. The ICFs were determined from a reference Si1-xGex alloy film by the conventional method, average intensity (AI) method and total number counting (TNC) method. In the case of SIMS, although the atomic fractions measured by oxygen ion beams were not quantitative due to severe matrix effect, the results by cesium ion beam were very quantitative. The quantitative analysis results by SIMS using MCs2+ ions are comparable to the results by XPS. In the case of XPS, the measurement uncertainty was highly improved by the AI method and TNC method.

High-Voltage LiNi0.5Mn1.5O4 Thin Film Cathode Prepared By RF Sputtering

Introduction Lithium ion battery is dominant in secondary battery market due to its long cycle life and high energy density compared to other batteries such as nickel hydride and lead acid batteries and thus has been widely used in electronic devices. However, present lithium ion battery, which uses olivine LiFePO4, spinel LiMn2O4 or layered LiCoO2 as cathode materials, cannot meet the requirement of the power sources for transportation applications. With the development of electric vehicles, lithium ion battery with higher energy density is needed. One of the effective ways to enhance the energy density of lithium ion battery is to employ high voltage cathode materials. LiNi0.5Mn1.5O4 cathode has received a great attention for its high potential plateau at around 4.7 V (vs. Li/Li+) and its low price due to enough manganese resource. In this work, LiNi0.5Mn1.5O4 cathode films were deposited by reactive radio-frequency (RF) sputtering on stainless steel substrate. The effects of post-annealing process on the crystallinity and electrochemical performance were examined. As the post-annealed temperature increases, the crystallinity of the thin film becomes better. However, the electrochemical properties did not show the corresponding results. The metal inter-diffusion between stainless steel and LiNi0.5Mn1.5O4film was observed in the annealing process at 600 ℃ or more. Experimental LiNi0.5Mn1.5O4 thin films were fabricated on Stainless Steel substrates. 400 nm-thick LiNi0.5Mn1.5O4 cathode layers were deposited by reactive sputtering using LiNi0.5Mn1.5O4 target. After the deposition, the cathode thin film on stainless steel was crystallized according to various post-annealing temperatures. The electrochemical cell consisted of a Li-metal foil counter electrode, and 1mol/L LiPF6 in a 1:1 solvent mixture of ethylene carbonate and diethyl carbonate as the electrolyte. The cells were assembled in an argon-filled glove box. The structure and crystallinity of the films were investigated using X-ray diffraction (XRD) with Cu Ka radiation. Charge / discharge tests were performed between 2.5 and 5.0 V in the current-rate of 0.05C. The secondary ion mass spectroscopy (SIMS) depth profile measurements were used to analyze the LiNi0.5Mn1.5O4thin films. Results and Discussion The XRD examination of the LiNi0.5Mn1.5O4 thin film on stainless steel substrate obtained from Rf-sputtering method confirmed the spinel crystal structure (Fig. 1). Charge / discharge profiles showed typical curves of spinels such as LiMn2O4 and LiNi0.5Mn1.5O4 at the 1st and 30th cycles (Fig. 2). Among the various post-annealed samples, the 500 °C sample exhibited the best characteristics. The low plateau at about 4 V corresponds to the redox reaction of Mn3+/Mn4+, while the high plateau at about 4.7 V corresponds to the redox reactions of Ni2+/Ni3+ and Ni3+/Ni4+. To investigate the inter-diffusion between the film and the substrate, SIMS depth profile measurements were performed on LiNi0.5Mn1.5O4 thin films at the different post-annealed temperatures (Fig. 3). Above 600 °C, Fe ion and Cr ion were observed in the LiNi0.5Mn1.5O4region. Conclusions Spinel LiNi0.5Mn1.5O4 thin films were successfully prepared on stainless steel substrates by sputtering method. The post-annealed temperature plays an important role in the formation of the LiNi0.5Mn1.5O4film. As the post-annealed temperature increased, the crystallinity of the thin film increased. However, at 600 °C or higher, inter-diffusion occurred between the substrate and the thin film, and secondary phases were formed. As a result, the electrochemical characteristics were deteriorated due to these characteristics. Figure 1