DC Sputtering Power Research Articles

High performance of Ag/AlN/Si Schottky diode: Study of the DC sputtering power effect on its electrical properties

The DC sputtering power (DCSP) effect on the chemical composition, structural and electrical properties of Ag/AlN/Si Schottky diode was studied. The AlN films grown on Si substrate were examined by X-ray diffraction (XRD), Fourier Transformed Infra-Red (FTIR), and Raman spectroscopy. The analyzes by XRD, FTIR and Raman show stability at the level of the structure and the qualitative chemical composition of the AlN layer for DCSP of 200 W and 400 W. However, the quantity of chemical compounds on the surface of AlN is affected by this variation. From Current-Voltage (I-V) measurements, the ideality factor (n), barrier height (φb), and series resistance (Rs) were extracted by adopting Cheung functions. Diodes with an AlN interlayer elaborated at 400 W have good rectifying behavior with n, Rs and φb of 3.11, 1930 Ω, and 0.93 eV, respectively. The enhancement of the Ag/AlN/Si diode performance was attributed to the reduction of undesirable impurities in the Ag/AlN interface as well as the morphological improvement of the AlN layer. Capacitance-Voltage (C-V) measurements showed that carrier donor concentrations are strongly affected by DC sputtering power. The elaborate structures may provide new materials with electrical properties having a wide range of applications in electronics and photovoltaic field.

Correlation of sputtering power with microstructure and ionic conductivity in lithium aluminum oxide thin films prepared by reactive co-sputtering

Li–Al–O thin films synthesized via the reactive magnetron co-sputtering have the potential to act as solid-state electrolytes in micro-batteries. In this paper, the constant RF power (155 W) and variable DC power (20–50 W) were applied to lithium (Li) and aluminum (Al) metal targets, respectively, in Ar/O2 atmosphere to produce films with adequate ionic conductivity. The influence of DC sputtering power on the composition, microstructure, band gap energy, ionic conductivity, and dielectric loss of films were studied in detail. X-ray photoelectron spectroscopy (XPS) showed a shift of the Li 1s peak towards higher binding energy with increasing DC power. X-ray diffraction (XRD) spectra confirmed the amorphous state for all as-deposited films, while the post-annealed films at 950 °C contain the γ-LiAlO2 phase. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images revealed that the increasing DC power had a significant impact on the film morphology, enlarging grain size and increasing surface roughness. Energy dispersive X-ray (EDX) spectroscopy showed that increasing the DC power increased the Al content. The optical properties were examined by ultraviolet–visible (UV–vis) spectroscopy, which indicated that increasing the Al content led to a blue shift of the absorption edge and an increase in the band gap energy (5.40–5.68 eV). Increasing the DC power resulted in an improvement of room-temperature conductivity by two orders of magnitude (∼2.85 × 10−9 S cm−1) and a decrease in the activation energy from 0.54 eV to 0.32 eV. These results suggest that composition and microstructure significantly affect the ionic transport in co-sputtered Li–Al–O films.

Characteristics of DLC films doped with multi-element alloy

Multi-element alloy doped diamond-like carbon (DLC) films were coated using sputtering with a (AlCrNbSiTiV) target. TEM and XRD results indicated DLC film had an amorphous compound feature incorporating polycrystalline phases around the face-centered cubic structure, which were embedded into the amorphous carbon matrix. The Raman spectra and mechanical characteristics of the DLC film sample were associated with concentration changes in the carbon and the multi-element alloy doped in the DLC films, which depended on the DC power. This investigation indicated that improved mechanical properties, including hardness and the elastic recovery rate, can be obtained from the multi-element alloy doped DLC film coated with proper DC sputtering power. These results demonstrated a proper DC power modifies the structure of multi-element alloy doped DLC film and improves its mechanical performance. This study should pave the way for the development of DLC film and elevate its application in various industries.

Optical Properties of Manufactured Mirrors Using DC Plasma Magnetron Sputtering Technique

This paper defines a method for sputtering high strength, extremely conductive silver mirrors on glass substrates at temperatures ranging from 20o to 22o C. The silver coated layer thicknesses in this work ranges from 7.5 to 16.1 nm using sputtering time from 10 to 30 min at power 25 W, 13.7 to 29.2 nm for time 10 to 30 min at 50 W, 15.7 to 26.4 nm for time 10 to 30 min at 75 W and 13.8 to 31.1 nm for time 10 to 30 min at 100 W. The optimum values of pressure and electrode gape for plasma sputtering system are 0.1 mbar and 5 cm respectively. The effect of DC sputtering power, sputtering duration or (sputtering time), and thickness on optical properties was investigated using an ultraviolet-visible spectrophotometer. The ultraviolet absorption of all coated layers was high, while the visible absorption was low. The transmittance is decrease with increase sputtering time and sputtering power. Highest values of reflection in visible region at 100 W and 20, 25 and 30 min are 46% to 97%. High value of band gap at 100 and 30 min while lower value at 25 W and 10 min.

Influence of Pulsed DC Sputtering Power on the Quality and Residual Stress of AlN Films on Si (100) Substrates

AbstractAluminum nitride (AlN) films are prepared on Si (100) substrates by pulsed direct current magnetron sputtering. The effect of sputtering power on the crystal quality, residual stress, surface morphology, and optical properties of AlN films is comprehensively studied using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscope, and ellipsometer. It is found that the AlN film quality is strongly impacted by the sputtering power. When the sputtering power increases to 3 kW, the full width at half maximum of the AlN (002) rocking curve decreases to 2.66°. And the film crystal quality does not change significantly when the sputtering power exceeds 3 kW. Fourier transform infrared spectrum analysis shows that with increasing sputtering power, the compressive stress of AlN films first increases and then decreases. The high sputtering power also results in smoother surface and better optical performance for the AlN films. This work can serve as an important reference for growing high‐quality AlN films on cost‐effective silicon (Si) substrates via sputtering, which can facilitate the development and commercialization of III‐nitride based photonics and electronics on AlN‐on‐Si substrates.

Pico-molar level detection of copper ion with extraordinarily high response by Ti-doped copper nitride fabricated via high power impulse magnetron sputtering

Various specific methods have been exercised in recent years to detect heavy metal ions in drinking water or body fluids for environmental as well as health safety. Likewise, development of a simple, fast, and robust method for copper ion (Cu2+) sensing is of paramount importance. Here, we demonstrate an effective Cu2+ sensor by exploiting the change in electrical conductivity of Ti-doped copper nitride (Cu3N) in presence of Cu2+ in solution. The Cu2+ sensor was fabricated with a Ti-doped Cu3N film deposited on indium-tin-oxide (ITO) coated quartz glass substrate by co-deposition method using high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering system simultaneously. DC sputtering power of Ti source was tuned from 0 W to 200 W with 50 W steps to achieve the Cu3N film with doping concentrations of 0, 0.19, 0.33, 0.87, and 1.6 at% respectively. Application of a diluted Cu2+ solution on the Ti-doped Cu3N film increases its electrical conductivity dramatically as manifested in the increase in current measured between two consecutive ITO electrodes beneath the thin film. The extraordinarily high copper sensitivity of the Ti-doped Cu3N film (1.6 at%) originated from the nitrogen-rich surfaces leads to detection of Cu2+ in water at as low as 8 pM concentration. The sensor exhibits not only high response but also a large linear dynamic range of 8 pM to 80 nM well below the maximum contaminant level goal for copper ion in drinking water. The high selectivity and reasonable cross-sensitivity of the sensor show potential commercialization in near future.

Tailored Hydrogen-Free Carbon Films by Tuning the sp2/sp3 Configuration

Carbon configuration is a critical factor in determining the electrical, tribological, and mechanical properties of carbon films. In this work, we synthesized carbon films on a silicate glass by sputtering a graphite target in an Ar atmosphere while varying the DC sputtering power. Using Raman spectroscopy and photoemission analysis, we found that the carbon films produced at low sputtering power consisted mainly of sp3 bonds, while sp2 carbon ordering became dominant as the sputtering power increased. The sp2/sp3 ratio of the carbon film controlled by the sputtering power is associated with two competing carbon deposition mechanisms: (1) collision between the incoming carbon ions and surface carbon atoms at low power (sub-plantation model) and (2) sp3-to-sp2 rehybridization caused by excessive kinetic energy of the incoming carbon ions at high power (thermal relaxation). As the sputtering power increased, the friction, adhesion, and energy dissipation decreased, despite negligible topographical variations, while the conductivity rapidly increased. We fabricated a triboelectric nanogenerator with high durability by utilizing the low friction properties of the sputtered carbon films. Our results show a straightforward and effective way to control the properties of carbon films, which can be used as promising coating films for frictionless protection.

Nonlinear saturated absorption properties of Ag-MoSe2 films by co-sputtering

In this paper, the Ag-MoSe2 films were prepared on quartz substrates by magnetron sputtering, and the influence of Ag doping on their morphology, optical band gap and nonlinear optical properties was studied. The SEM images show images show the relative low content of silver, and the Se precipitation. The nonlinear absorption properties were measured by Z-scan technique, indicating the saturable absorption behavior. Under different DC sputtering power, the nonlinear absorption coefficient decreased and then increased. The significant nonlinear absorption is demonstrated with the coefficient of ~ 10-4 cm/W. The proposed Ag-MoSe2 film is a promising candidate for the application in optoelectronic devices.

Negative magnetoresistance in iron doped TiN thin films prepared by reactive magnetron sputtering

Iron doped titanium nitride thin films were prepared by RF/DC magnetron sputtering of titanium and iron targets in the presence of argon and nitrogen gasses. Iron concentration in the films was controlled by adjusting the DC power of the sputtering gun whereas the RF power for the titanium target was kept constant for all the films. Spectrophotometry of the grown films revealed a reduction in the bandgap with the increase in the iron concentration in the films. X-ray photoelectron spectroscopy of the films confirmed the presence of iron and the increase in its concentration with the increase in the DC sputtering power. The surface roughness of the films slightly increased with the increase in the iron concentration. All the grown films were n-type semiconductors and the carrier concentration increased with the increase in iron concentration. Positive magnetoresistance was observed in undoped or low-doped titanium nitride films, whereas negative magnetoresistance was observed in the films with high iron concentration, which was due to the formation of ferromagnetically aligned magnetic polarons.

The frequency of pulsed DC sputtering power introducing the graphitization and the durability improvement of amorphous carbon films for metallic bipolar plates in proton exchange membrane fuel cells

Amorphous carbon (a-C) films have been coated on the metallic bipolar plates (BPPs) in Proton Exchange Membrane Fuel Cells (PEMFCs) to improve the corrosion resistance and the interfacial electrical conductivity of metallic BPPs. However, the durability of a-C in the harsh environments of PEMFCs is still confronted with enormous challenges. In this paper, a-C films are prepared on SS316L BPPs via pulsed DC sputtering power with different frequency and the further understanding of corresponding mechanism on the structure and the performance of a-C is revealed. The results indicate that the compactness of films is enhanced significantly by pulsed DC power. Moreover, the moderate frequency is beneficial to the formation of nanographite clusters, which are embedded into a-C and reduce the interfacial contact resistance (ICR). Furthermore, the analyses of corrosion performance of the films conclude that the embedded nanographite clusters form micro primary cell with a-C and protect a-C from corrosion. The ICR of the film prepared at 200 kHz after corrosion for 200 h at 0.84 Vvs.SHE is 2.44 mΩ⋅cm2, which exhibits ultra-low ICR and achieves excellent durability during the operating procedures of PEMFCs. This study is beneficial to enhance the lifetime of a-C and promote the commercialization of PEMFCs.

Electrical and optical properties of copper oxide thin films prepared by DC magnetron sputtering

Copper oxides (CuO, Cu2O) have promising application potential in sensors or solar cells. In this study, copper oxide thin films were prepared by reactive DC magnetron sputtering using helicon plasma. A pure copper target was sputtered with Ar gas in an O2 atmosphere with a DC sputtering power in the range of 10–40 W, while the other fabrication conditions were kept constant. X-ray diffraction and x-ray photoelectron spectroscopy were used to investigate the effect of the sputtering power on the structure and the chemical state of the fabricated films. Atomic force microscopy was used to determine the relationship between the film's surface morphology and its structure. Hall effect measurements were employed to measure the semiconductor's properties, and the optical bandgap was determined by UV-Vis spectroscopy. The copper oxide film could be continuously tuned from n-type CuO to p-type Cu2O by changing the DC magnetron sputtering power.

Molybdenum incorporated Cu1.69ZnSnS4 kesterite photovoltaic devices with bilayer microstructure and tunable optical-electronic properties

Molybdenum (Mo) incorporated Cu1.69ZnSnS4 (CZTS) absorber has been deposited onto Mo-coated soda lime glass (SLG) by co-sputtering of Mo and non-stoichiometric quaternary compound targets. After sulfurization at 600 °C, Mo incorporation into CZTS was confirmed by X-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS). From the observed shifts for the (1 1 2) and (2 2 0) peaks, both lattice parameters a and c of the CZTS unit cell were found to decrease with increasing Mo incorporation suggesting cationic substitution by Mo. The Mo incorporated CZTS has a bilayer microstructure in which the lower sub-layer adjacent to the substrate has a smaller grain size and higher porosity than the upper sub-layer. The lower sub-layer is also richer in Mo and has a graded Mo profile. Sheet resistance measurements on Mo incorporated CZTS films deposited on SLG and on quartz show resistivity that decreases with the amount of Mo in CZTS and Mo acts as an acceptor dopant. The energy band gap of CZTS on SLG increases from 1.38 eV to about 1.68 eV as a result of Mo incorporation and the absorbance of Mo incorporated CZTS is increased for wavelengths shorter than 600 nm. When Mo is co-deposited at the optimized DC sputtering power of 10 W, Mo incorporated CZTS/CdS solar cells attain a maximum power conversion efficiency (PCE) of 5.49% versus 1.63% for the reference device under 1 Sun AM 1.5 illumination. Device efficiency enhancement is due to back surface field, increased carrier concentration and reduced band tailing.

Exchange bias and two steps magnetization reversal in porous Co/CoO layer

In this paper Co/CoO thick layers (hundreds of nanometers) of different porosity and oxidation degree were prepared in a magnetron sputtering deposition process by tailoring the DC sputtering power, as well as the process gas and target composition. The control of the synthesis parameters allowed the nanostructuration of the films with a singular distribution of closed pores and a controlled amount of CoO. We observed an exchange bias field of 2.8 KOe for porous Co/CoO composites, similar to Co/CoO bilayers but for coatings thicker than 300 nm. Besides, it was observed that the coating presents bistable magnetic features when cooled under zero field conditions as a result of the unusual exchange coupling.

Nonlinear absorption properties and excited-state charge-transfer dynamics of Er doped ZnO films

This work reports on the nonlinear optical properties of Er doped ZnO (EZO) films, measured by the Z-scan technique with different laser parameters (pulse width, wavelengths and energy). The nonlinear absorption mechanism of EZO films is analyzed by a singlet state three and four-level model, respectively. The effect of the direct current sputtering power of EZO films on the nonlinear optical properties was studied. From the results, the samples show the self-focusing effect and two photon absorption (TPA) induced excited state reverse saturable absorption (RSA) behavior. Under the different laser parameter excitation, it has been determined that the TPA induced saturable absorption (SA) or RSA properties for EZO films with 8 W dc sputtering power. Moreover, these findings indicate that free carrier density increases with Er doping and this behavior leads to excited state absorption. In addition, the ultrafast dynamics of EZO films have been investigated using the two-color pump-probe (TCPP) technique with 325, 380 and 400 nm wavelength excitation and probing over a broad range in the visible region. The decay of the positive signal is found to be biexponential, which we have assigned to the pump-induced deep-level (DL) or excited state absorption. We also present experimental results that the few decade picosecond component has been assigned to vibrational relaxation in the excited electronic states, and the slow components represent the decay from singlet excited state to the ground state ( 1.2 ns). Moreover, these findings indicate that the excitation wavelength increases and the detection wave band widens. Our results show that EZO films are a promising candidate in further optoelectronic device applications.

Composition, Microstructure, and Electrical Performance of Sputtered SnO Thin Films for p-Type Oxide Semiconductor.

p-Type SnO thin films were deposited on a Si substrate by a cosputtering process using ceramic SnO and metal Sn targets at room temperature without adding oxygen. By varying the dc sputtering power applied to the Sn target while maintaining a constant radio frequency power to the SnO target, the Sn/O ratio varied from 56:44 to 74:26 at the as-deposited state. After thermal annealing at 180 °C for 25 min under air atmosphere using a microwave annealing system, the films were crystallized into tetragonal SnO when the Sn/O ratio increased from 44:56 to 57:43. Notably, the metallic Sn remained when the Sn/O ratio was higher than 55:45 at an annealed state. When the ratio was lower than 55:45 at the annealed state, the incorporated Sn fully oxidized to SnO, making the films useful p-type semiconductors, whereas the films became metallic conductors at higher Sn/O ratios. At the Sn/O ratio of 55:45 at the annealed state, the film showed the highest Hall mobility of 8.8 cm2 V-1 s-1 and a hole concentration of 5.4 × 1018 cm-3. Interestingly, the electrical conduction behavior showed trap-mediated hopping when the Sn metal was cosputtered, whereas the single SnO film showed regular band conduction behavior. The residual stress effect could interpret such property variation originated from the sputtering power and postoxidation-induced volumetric effects. This report makes a critical contribution to the in-depth understanding of the composition-structure-property relationship of this technically important thin film material.

Fabrication and electrochemistry characteristics of nickel-doped diamond-like carbon film toward applications in non-enzymatic glucose detection

This research work focused on the fabrication of nickel-doped diamond-like carbon (DLC) films and their characteristics including of surface morphology, microstructure, and electrochemical aiming at applications in non-enzymatic glucose detection. Novel nanodiamond target was employed in unbalanced magnetron radio-frequency co-sputtering process to prepared high quality Ni-doped DLC thin film at room temperature. TEM analysis reveals a highly uniform distribution of Ni crystallites in amorphous carbon matrix with fraction ranged from 3 to 11.5 at.% which is considered as active sites for the glucose detection. Our cyclic voltammetry measurements using 0.1 M H2SO4 solution demonstrated that the as-prepared Ni-doped DLC films possess large electrochemical potential window of 2.12 V, and this was also observed to be significantly reduced at high Ni doping level owing to lower sp3 fraction. The non-enzymatic glucose detection investigation indicates that the Ni-doped DLC thin film electrode prepared under 7 W of DC sputtering power on Ni target possesses good detecting performance, high stability, and high sensitivity to glucose concentration up to 10 mM, even with the existence of uric acid and ascorbic acid. The peak current was observed to be proportional to glucose concentration and scanning rate, demonstrating highly reversibility redox process of the film electrode and glucose.

Plasma sputtering depositions with colloidal masks for fabrication of nanostructured surfaces with enhanced photocatalytic activity

Titanium oxide/silicon oxide (TiO2/SiO2) 2D patterns were obtained by magnetron sputtering depositions of Ti on close-packed and size-reduced colloidal masks on Si and quartz substrates, followed by mask lift-off and ending with thermal oxidation. The physical processes involved in growing 2D Ti patterns and their oxidation are analyzed. For the magnetron sputtering deposition, two regimes are considered: the low-pressure regime when the flux of sputtered atoms is anisotropic, and the high-pressure regime, when the flux of sputtered atoms is isotropic due to frequent collisions. Moreover, magnetron sputtering operation modes, such as dc sputtering and high power impulse sputtering, are compared. The changes in pattern size and morphology determined by the oxidation of the Ti patterns and Si substrate are analyzed. The hydrophilicity induced by UV-light irradiation and the visible-light photocatalytic activity towards the degradation of the methylene blue of the fabricated TiO2/SiO2 patterns were considerably higher when compared to the performances of uniform TiO2 films.

Ultrafast carrier dynamics and third order nonlinear optical properties of aluminum doped zinc oxide (AZO) thin films

Aluminum doped zinc oxide (AZO) thin films were fabricated by simultaneous RF/DC magnetron sputtering technique on sapphire (Al2O3) substrate with different DC sputtering power 2, 6, 8 and 10 W respectively. The sputtered thin films were annealed at 350 °C in order to improve the crystal quality. AZO thin films are systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS spectrometer for structural and optical properties. XRD patterns show that all sputtered thin films are well crystallized with hexagonal wurtzite structure. SEM images reveal the average crystallite sizes are increased after doping Al in ZnO which agreed with the calculated values from XRD. All thin films possess high optical transmittance in visible region and optical band gap values are relatively increased with Al concentration. The ultrafast transient absorption (TA) of AZO was analyzed by femtosecond pump-probe spectroscopy. The kinetic TA curves were fitted by tri-exponential decay function and obtained decay time constants are found to be in few picosecond and nanosecond range for ultrafast and slow processes respectively. Third order nonlinear optical absorption and refraction coefficients were investigated by using Z-scan technique. The observed nonlinear coefficients are enhanced with Al concentration in ZnO.

Aluminium induced texturing of glass substrates with improved light management for thin film solar cells

Aluminium induced texturing (AIT) method has been used to texture glass substrates to enhance photon absorption in microcrystalline thin film Si solar cells. In this process, a thin Al film is deposited on a glass substrate and a non-uniform redox reaction between the glass and the Al film occurs when they are annealed at high temperature. After etching the reaction products, the resultant glass surface presents a uniform and rough morphology. In this work, three different textures (σrms~85, ~95, ~125nm) have been achieved by tuning the dc sputtering power and over them and over smooth glass, pin microcrystalline silicon solar cells have been fabricated. The cells deposited over the textured substrates showed an efficiency improvement in comparison to the cells deposited over the smooth glass. The best result was given for the glass texture σrms~125nm that led to an average efficiency 2.1% higher than that given by the cell deposited on smooth glass.

Structural and opto-electrical properties of Al doped ZnO sputtered thin films

Transparent and conductive aluminum-doped zinc oxide (AZO) thin films with high preferential c-axis orientation have been deposited on glass substrates by radio frequency magnetron sputtering method of ZnO and DC magnetron sputtering of Al. Structural, surface morphology, optical and electrical properties of ZnO thin films were studied by X-ray diffraction, scanning electron microscope, ultraviolet–visible spectrophotometer, surface plasmon spectroscopy and Hall effect measurements. The results show that AZO films are polycrystalline and exhibit the hexagonal wurzite crystal structure with a preferred orientation along (002) direction. When DC sputtering power supplied to Al target increases, the crystallinity decreases while the electrical resistivity increases. The average measured transmittance exceeded 75 % in the visible range for all AZO thin films. The band gap values increase with decreasing the Al concentrations.