Optimized Sputtering Conditions Research Articles

Prediction by a hybrid machine learning model for high-mobility amorphous In2O3: Sn films fabricated by RF plasma sputtering deposition using a nitrogen-mediated amorphization method

In this study, we developed a hybrid machine learning technique by combining appropriate classification and regression models to address challenges in producing high-mobility amorphous In2O3:Sn (a-ITO) films, which were fabricated by radio-frequency magnetron sputtering with a nitrogen-mediated amorphization method. To overcome this challenge, this hybrid model that was consisted of a support vector machine as a classification model and a gradient boosting regression tree as a regression model predicted the boundary conditions of crystallinity and experimental conditions with high mobility for a-ITO films. Based on this model, we were able to identify the boundary conditions between amorphous and crystalline crystallinity and thin film deposition conditions that resulted in a-ITO films with 27% higher mobility near the boundary than previous research results. Thus, this prediction model identified key parameters and optimal sputtering conditions necessary for producing high-mobility a-ITO films. The identification of such boundary conditions through machine learning is crucial in the exploration of thin film properties and enables the development of high-throughput experimental designs.

Enhanced Raman spectroscopy analysis for contamination detection on microelectronic devices using gold nanoclusters grown by DC magnetron sputtering

Surface-enhanced Raman spectroscopy (SERS) is one of the most powerful analytical techniques for the identification of molecules in microelectronics industry for failure analysis protocols. Surface-enhanced Raman spectroscopy (SERS) is one of the most powerful analytical techniques for the identification of molecules in the microelectronics industry for failure analysis protocols. In this work, dry-processed gold nanoclusters were prepared by magnetron sputtering deposition to promote the enhancement of the Raman signal from selected common polymers found in the hard disk drive as surface contamination. The optimized sputtering conditions were applied for SERS on poly-carbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), and high-density polyethylene (HDPE). The Raman spectrum showed the average Raman signal intensity gain at about 114%, 78%, 254%, and 226%, respectively. The SERS with gold nanoclusters, prepared by magnetron sputtering, demonstrates that this method is a clean, simple, highly performing analytical method for failure analysis and can be an alternative method over the use of colloidal gold nanoparticles for contamination investigation in industrial failure analysis procedures, where the sample cleanness during the analysis is critical, as in the microelectronic industry.

Co-evaporated p-i-n perovskite solar cells with sputtered NiOx hole transport layer

Metal oxides have long been used as charge transport layers in thin film solar cells due to their suitable energy band levels, high charge carrier mobilities, and excellent long-term stability. One example is non-stoichiometric nickel oxide (NiOx), a hole transport material which can be deposited in a conformal, scalable, and solvent-free manner via sputtering. However, sputtered NiOx has only ever been combined with spin-coated perovskite films in perovskite solar cells (PSCs). Here we report the fabrication of the first co-evaporated PSCs with sputtered NiOx as the hole transport layer. We reveal how the amount of argon gas used during sputtering affects important physical properties such as hole conductivity, visible light transmittance, and suitability of the NiOx surface for perovskite nucleation and growth. Optimized sputtering conditions led to CH3NH3PbI3 (MAPbI3) PSCs with an 18.6% power conversion efficiency (PCE), which was further increased to 19.5% by adding a spiro-TTB interlayer between NiOx and MAPbI3. We also show that removing the NiOx annealing step only reduced the device PCE by 1%, paving the way toward low-temperature deposition of metal oxide transport layers. This work exhibits the versatility of NiOx sputtering and perovskite evaporation as a powerful combination for solvent-free and low-temperature fabrication of highly efficient PSCs.

Study of Ni–Cr / CrN bilayer thin films resistor prepared by magnetron sputtering

In this study, we prepare bilayer Ni–Cr/CrN films. A Ni–Cr resistive thin film was prepared by DC sputtering from targets of Ni0.8-Cr0.2 casting alloy. A CrN protection thin film was prepared based on optimum sputtering conditions of the Ni–Cr film, which was made by DC and RF magnetron co-sputtering from targets of Ni0.8-Cr0.2 casting alloy and chromium. The electrical properties and microstructures of the resistive films at different annealing temperatures were investigated. The phase evolution, microstructural and composition of Ni–Cr and NiCr/CrN films were characterized by X-ray diffraction (XRD), field-emission transmission electron microscopy (HRTEM) and auger electron spectroscopy (AES). The results indicated that the resistivity of the bilayer Ni–Cr/CrN films is higher than Ni–Cr films. When the annealing temperature was set to 300 °C, the bilayer Ni–Cr/CrN films exhibited a resistivity ∼303 μΩ cm with the smallest temperature coefficient of resistance (TCR) of −3 ppm/°C. However, the Ni–Cr films that annealed at 300 °C showed a resistivity of ∼210 μΩ cm, with a TCR of 13 ppm/°C. In addition, the TCR and resistivity variation rate of CrN protective coating layer on the Ni–Cr films after high temperature testing at 150 °C up to 100 h was done. The results show that the average change rate of the TCR for bilayer Ni–Cr/CrN films is lower than single Ni–Cr films.

Nano-mechanical properties of Cr-Zr-Nb-N medium entropy alloy films produced by reactive sputtering

Protective thin films have gained extensive applications in various industries, especially in machining. The present work investigates the structure-mechanical properties relations of Cr-Zr-Nb-N medium entropy films deposited by sputtering. First, chemical analysis (by means of EDS, GI-XRD and Raman spectroscopy), morphology (by SEM) and topology (by means of AFM) of the coatings are studied. By applying graphical methods, average and root mean square roughness, skewness, kurtosis, fractal dimension and texture characteristics are extracted from 2D-AFM images. In addition, hardness, toughness and friction coefficient of the films are reported by employing nano-indentation and nano-scratch tests. Finally, optimum sputtering conditions (substrate temperature = 500 ̊C, nitrogen flow rate = 15 sccm and − 10 V ≤substrate bias voltage≤ − 70 V) and fractal parameters necessary to obtain wear-resistant films are presented. The thin film deposited under the optimum condition demonstrates high hardness (21.3 GPa), toughness (H/E = 0.096 and H3/E2 = 0.195 GPa) and minimum wear characteristics (CoF < 0.2, wear width = 479 nm and wear depth = 56 nm).

Wide-range tunable Ba0.7Sr0.3TiO3 films capacitors on LiNbO3 substrates

Ba0.7Sr0.3TiO3 (BST) films on Y-cut LiNbO3 substrates are investigated to realize wide-range tunable BST capacitors. The performances of the BST films are improved by the optimal magnetron sputtering conditions. It is found that the permittivity tunability of the BST capacitor reaches 300% under an applied voltage of 5 V. Moreover, the film has a high dielectric constant 2700 under an applied voltage of 0 V, and the Q value of the BST capacitor exceeds 3000. The results demonstrate that the BST film on the LiNbO3 substrate has potential as a wide-range tunable capacitor for tunable surface acoustic wave filters.

Effect of RF power on AlN film crystallinity in low pressure range using Ar-20%N2 gases by magnetic mirror-type magnetron cathode

Effect of radio frequency (RF) power on aluminum nitride (AlN) film crystallinity has been studied under low gas pressure of 0.1 Pa and low RF power of 3 W with Ar-20%N2 gas by a proposed balanced magnetron cathode with a high plasma production efficiency. The gas pressure and the RF power dependences of AlN film crystallinity show that the c-axis oriented AlN films can be obtained only at 50 W and 100 W in 0.1 Pa. The AlN film crystallinity was not promoted in the low RF power range of <50 W. An Ar-rich sputtering condition at 0.1 Pa induced the Al–Al bonds in the deposited films in a high RF power range of 15 W. The control of the total flux balance between Al and nitrogen atoms at the substrate surface is important to design the optimum sputtering condition at 0.1 Pa.

Inverted organic photovoltaics using highly transparent and flexible InGaON/AgTi/InGaON multilayer electrodes

The inverted organic solar cell (IOSC) supported on an optically transparent and mechanically flexible oxynitride/metal/oxynitride substrate is receiving increasing attention owing to its light weight, flexible, and cost-effective design, compared to the conventional oxide-based solar cells. To develop an efficient IOSC, technical issues related to charge carrier transport and the transmittance of the conventional oxide electrode need to be solved. Herein, we report a highly transparent cathode for a highly efficient inverted organic solar cell using InGaON/Ag–Ti/InGaON multilayer electrodes. The In2O3 and GaN targets are co-sputtered to fabricate the multicomponent conductive oxynitride films. The sheet resistance of InGaON in optimized sputtering conditions is about 53.63 Ω/□, with the transmittance of 88.12%. The optimal InGaON/Ag–Ti/InGaON configuration (35/12/35 nm) showed the low sheet resistance of 5.7 Ω/□, and higher transmittance of about 96.8% as a whole InGaON/Ag–Ti/InGaON electrode. The multilayer electrode showed superior mechanical property in bending and twisting for 10,000 cycles with no resistance change. Furthermore, the inverted organic solar cell with the deposited layers of InGaON/Ag–Ti/InGaON–ZnO–Active layer–MoO3–Ag exhibited the higher power conversion efficiency of 8.63%, indicating that the InGaON/Ag–Ti/InGaON cathode is a promising candidate for substitution for the conventional oxide electrode.

High-Quality Sputtered BiFeO3 for Ultrathin Epitaxial Films

BiFeO3 films were grown by RF magnetron sputtering with various O2 gas flow ratios and substrate temperatures. The optimal sputtering conditions for a slightly excess Bi content produced high-quality parameters: an atomically flat surface (Ra < 0.4 nm), low leakage current (Jc < 10–6 A/cm2), high ferroelectric polarization (72 μC/cm2//[001]pc), and large exchange bias (∼140 Oe). In addition to these typical characterizations, the following two advanced analyses were performed: (i) The lattice constant was identified by Bragg’s diffraction specific to a space group of R3c using X-ray diffraction; it was precisely determined as an expanded a-axis (abulk = 0.568 → aepi = 0.572 nm) and a shrunk c-axis (cbulk = 1.398 → cepi = 1.373 nm). (ii) The ferroelectricity was analyzed by first-order reversal curve (FORC) diagrams, which revealed that ferroelectric switching was packed in a narrow electric field area; an internal electric field in the film body was not observed despite the fact that the BiFeO3 films were as-grown samples. A 3 nm thick BiFeO3 film with a continuous and flat surface/interface was confirmed over a wide area. The crystal symmetry might be identified as a space group of R3c in the case of the 3 nm thick film by comparing the nanobeam selected area electron diffraction patterns with the patterns based on structural calculations. The ferroelectricity might be confirmed by the piezoresponse force microscopy of a 2 nm thick BiFeO3 epitaxial film, owing to the optimal condition of low Jc and uniform ferroelectric switching properties. Furthermore, a 0.4 nm thick ultrathin BiFeO3 film was confirmed to be a continuous one-unit cell perovskite (∼0.4 nm) layer, owing to the optimal condition of low Ra. This study provides a method for investigating the crystal symmetry that affects the multiferroic properties of ultrathin films, which can be used as barrier layers in multiferroic tunnel junctions for highly functional sensors.

Effect of RF Power on the Physical Properties of Sputtered ZnSe Nanostructured Thin Films for Photovoltaic Applications.

Zinc selenide (ZnSe) thin films were deposited by RF magnetron sputtering in specific conditions, onto optical glass substrates, at different RF plasma power. The prepared ZnSe layers were afterwards subjected to a series of structural, morphological, optical and electrical characterizations. The obtained results pointed out the optimal sputtering conditions to obtain ZnSe films of excellent quality, especially in terms of better optical properties, lower superficial roughness, reduced micro-strain and a band gap value closer to the one reported for the ZnSe bulk semiconducting material. Electrical characterization were afterwards carried out by measuring the current–voltage (I-V) characteristics at room temperature, of prepared “sandwich”-like Au/ZnSe/Au structures. The analysis of I-V characteristics have shown that at low injection levels there is an Ohmic conduction, followed at high injection levels, after a well-defined transition voltage, by a Space Charge Limited Current (SCLC) in the presence of an exponential trap distribution in the band gap of the ZnSe thin films. The results obtained from all the characterization techniques presented, demonstrated thus the potential of ZnSe thin films sputtered under optimized RF plasma conditions, to be used as alternative environmentally-friendly Cd-free window layers within photovoltaic cells manufacturing.

Large-area CsPbBr3 perovskite films grown with effective one-step RF-magnetron sputtering

In this work, we demonstrated the large-area film growth of all-inorganic perovskite CsPbBr3 with semiconductor industry compatible radio frequency magneton sputtering technology. This approach avoids the use of toxic organic solvents, which are required extensively for the solution growth process of these perovskite films. Even on ordinary glass substrates, the CsPbBr3 film of 100 cm2 with a single phase and ultra-smooth surface can be grown under optimized sputtering conditions, among which the substrate temperature is proved very important. Temperature-dependent photoluminescence spectra and femtosecond transient absorption spectra studies show that no subband defect levels are observed in such perovskite films. The temperature-dependent resistivity measurement exhibits a typical thermally activated electrical behavior, and a bandgap of 2.24 eV is obtained, which is consistent with the optical measurements. Therefore, both the optical and electrical studies indicate that the CsPbBr3 film with high optical quality can be grown with effective one-step sputtering technology.

Magnetron-sputtered amorphous V2O5 hole injection layer for high performance quantum dot light-emitting diode

We developed radio frequency (RF) magnetron sputtered amorphous vanadium pentoxide (V2O5) film to use in place of typical PEDOT:PSS or solution-processed metal oxide hole injection layer (HIL) in quantum dot light-emitting diodes (QLEDs). The electrical, optical, and chemical properties of the sputtered V2O5 HIL were correlated with the oxygen flow rate at room temperature. At optimized sputtering conditions, the V2O5 film showed a high optical transparency of 91.93% in the visible wavelength region and a work function of 4.73 eV, which is suitable for HIL in QLEDs. We also investigated the performance of QLEDs with sputtered V2O5 HIL as a function of oxygen flow rate. The QLEDs with optimized V2O5 HIL exhibited a maximum luminance of 198,542 cd/m2, a turn-on voltage of 1.7 V, a max external quantum efficiency of about 8.3%, and a current efficiency of 20.3 cd/A, thereby making it comparable to typical PEDOT:PSS HIL-based QLEDs. The successful operation of QLEDs with sputtered V2O5 as HIL demonstrated that it could be used instead of other materials for next-generation large-area QLED displays.

Comprehensive study of crystalline AlN/sapphire templates after high-temperature annealing with various sputtering conditions

High-quality AlN/sapphire templates were fabricated by the combination of sputtering and high-temperature (HT) annealing. The influence of sputtering parameters including nitrogen flux, radio frequency power, and substrate temperature on the crystalline quality and surface morphology of annealed AlN films were investigated. With lower substrate temperature, lower power, and lower N2 flux, the full width at half maximum of the X-ray rocking curve for AlN (0002) and (10 2) were improved to 97.2 and 259.2 arcsec after high-temperature annealing. This happens because the increased vacancy concentration of sputtered AlN films can facilitate the annihilation of dislocations by increasing the recovery rate during HT annealing. Step and step-bunching morphologies were clearly observed with optimized sputtering conditions.

Study of piezoelectric behaviour of sputtered KNbO3 nanocoatings for flexible energy harvesting

Novel potassium niobate (KNbO3) nanocoatings were sputtered on polyethylene naphthalate (PEN) substrates at different sputtering voltages and concentrations of sputtering gas. The relations growth time - thickness and sputtering voltage-deposition speed were established and the vacuum deposition modes were optimized. This was realized, in order to correlate the microstructure, surface morphology and the growing conditions for the nanosized KNbO3 films. Uniform coatings with variety of thicknesses were obtained without overheating degradation of the substrates at process parameters Us and PAr varying from 0.6 kV to 0.9 kV and from 1 × 10−2 Torr to 9 × 10−3 Torr, respectively. New Al/KNbO3/Al energy harvesting element was fabricated and tested on tension-compression cycles. For the samples, showing the lowest surface roughness of the KNbO3 film (3.6%), maximum piezoelectric voltage of 431 mV was measured at loading up to 3 kg. Basic electric parameters, such as capacitance, contact and bulk resistance of the piezoelectric element, involving KNbO3 film, produced at the optimum sputtering conditions, were measured as a function of the applied mass load. Output electrical power of 2.324 μW was obtained at maximum mechanical loading, which is comparable with the results for lead-containing thin film harvesters. Theoretical analysis of the novel elements was made based on their dielectric behaviour in terms of polarization type. They were connected to passive power management system for operation as an independent power supply for low-power electronics.

Photovoltaic properties of low-damage magnetron-sputtered n-type ZnO thin film/p-type Cu2O sheet heterojunction solar cells

The photovoltaic properties of Cu2O-based heterojunction solar cells were improved using an n-type layer composed of thin films in a binary oxide semiconductor. This layer was prepared by a low-damage deposition method that applies a system for multi-chamber radio frequency (r.f.) power superimposed direct current (d.c.) magnetron sputtering. For an Al-doped ZnO (AZO)/n-ZnO/p-Cu2O heterojunction solar cell prepared using r.f. power superimposed d.c magnetron sputtering, we achieved the highest efficiency yet reported (3.22%) by optimizing sputtering conditions such as the substrate-target distance and the r.f.:d.c. power ratio. This value represents characteristics that exceed those of AZO/Cu2O solar cells having a similar structure based on r.f. power superimposed d.c magnetron sputtering.

Improvement on Fully Filled Through Silicon Vias by Optimized Sputtering and Electroplating Conditions.

The high reliability of electroplating through silicon vias (TSVs) is an attractive hotspot in the application of high-density integrated circuit packaging. In this paper, improvements for fully filled TSVs by optimizing sputtering and electroplating conditions were introduced. Particular attention was paid to the samples with different seed layer structures. These samples were fabricated by different sputtering and treatment approaches, and accompanied with various electroplating profile adjustments. The images were observed and characterized by X-ray equipment and a scanning electron microscope (SEM). The results show that optimized sputtering and electroplating conditions can help improve the quality of TSVs, which could be interpreted as the interface effect of the TSV structure.

Sensitive Five-Fold Local Symmetry to Kinetic Energy of Depositing Atoms in Cu-Zr Thin Film Growth.

We have investigated the glass formation ability of Cu-Zr alloy by molecular dynamics simulation of the deposition process. The atomistic structures of ZrxCu100−x metallic glass films have been systematically examined under the growth conditions of hypereutectic-eutectic, near-eutectic, and hypoeutectic regions by the radial distribution function and simulated X-ray diffraction. The structure analysis using Voronoi polyhedron index method demonstrates the variations of short-range order and five-fold local symmetry in ZrxCu100−x metallic glass films with respect to the growth conditions. We manifest that the five-fold local symmetry is sensitive to the kinetic energy of the depositing atoms. There is positive correlation between the degree of five-fold local symmetry and glass forming ability. Our results suggest that sputtering conditions greatly affect the local atomic structures and consequential properties. The glass forming ability could be scaled by the degree of five-fold local symmetry. Our study might be useful in optimizing sputtering conditions in real experiments, as well as promising implications in material design of advanced glassy materials.

High Ferroelectricities and High Curie Temperature of BiInO3PbTiO3 Thin Films Deposited by RF Magnetron Sputtering Method☆☆Supported by the National Natural Science Foundation of China under Grant No 11304160, the Special Fund for Public Interest of China under Grant No 201510068, and the NUPTFC under Grant No NY215111.

Properties of ferroelectric xBiInO3-(1 − x)PbTiO3 (xBI-(1 − x)PT) thin films deposited on (101) SrRuO3/(200) Pt/(200) MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated. The structures of the xBI-(1 − x)PT films are characterized by x-ray diffraction and scanning electron microscopy. The results indicate that the thin films are grown with mainly (001) orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process. The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents, 2 mol% La2O3 is doped in the targets. The P–E hysteresis loops show that the optimized xBI-(1 − x)PT (x = 0.24) film has high ferroelectricities with remnant polarization and coercive electric field . The Curie temperature is about 640 °C. The results show that the films have optimum performance and will have wide applications.

Optimized Growth of Gallium Oxide Thin Films Using Different Synthesis Processes

This paper investigates the optimized sputtering conditions for high quality gallium oxide (Ga2O3) thin films while maintaining a strong uniformity within a specific surface area. The research also analyzes the crystal structure and the morphology of gallium oxide (Ga2O3) thin films. We report a comprehensive investigation of two different types of Ga2O3 synthetization processes: (1) direct deposition using radio frequency (RF) magnetron sputter technique and (2) thermal oxidation of gallium nitride (GaN) samples. A detailed comparison is presented in terms of material characterization, surface analysis and electrical performance for each of the synthetization processes. X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and x-ray diffraction (XRD) are employed to study the gallium oxide (Ga2O3) epi-layers on each of the samples. Based on the analysis, Ga2O3 compound is found on all samples with a binding energy ranging from 21 eV to 21.38 eV. Depending on the synthetization process, the thickness varied from 20 nm to 100 nm for RF sputtering process and a maximum of ~ 400 nm for thermal oxidation method. Additionally, the observations revealed that Ga2O3 is formed on the surface, as well as inside the gallium nitride (GaN) film after thermal oxidation. Crystal features are observed on the surface of each of the samples after annealing treatment while XRD analysis showed the presence of the beta (β) polymorph for the annealed samples. After thorough characterization, radio frequency sputtering technique proved to be superior due to its higher purity level and ability to create polycrystalline structures by adding temperature during deposition.

Microstructure‐Mechanical Property Correlation in Size Controlled Nanocrystalline Molybdenum Films

The authors report on the microstructure, crystallography, and mechanical properties of size controlled nanocrystalline (nc) molybdenum (Mo) films deposited by sputtering. The nc‐Mo films of ≈100 nm thick with a variable microstructure are deposited under variable argon (Ar) sputtering pressure (PAr), which is varied in the range of 3–25 mTorr. X‐ray diffraction analyses indicate that the nc‐Mo films exhibit (110) preferential growth. However, the crystal‐quality degradation occurs for Mo films deposited at higher PAr due to difference in the adatom mobility. The average crystallite size (d) of the nc‐Mo films is in the range of 5–20 nm; size decreases with increasing PAr. The effect of sputtering pressure is significant on the microstructure, which in turn influences the mechanical characteristics of Mo films. The hardness (H) and modulus of elasticity (Er) of nc‐Mo films deposited at lower PAr are higher but decreases continuously with increasing PAr. Under optimum sputtering conditions, the best mechanical characteristics obtained for Mo films are: H = 25 GPa, Er = 360 GPa, H/Er = 0.07, and H3/ = 0.13 GPa. A size‐microstructure‐mechanical property correlation in nc‐Mo films is derived based on the results presented and discussed.