RF Reactive Sputtering Research Articles

Tuning optical and ferromagnetic properties of thin GdN films by nitrogen-vacancy centers

AlN/GdN/AlN double heterostructures were grown on c-sapphire substrates using a reactive rf sputtering method under high vacuum conditions. The optical absorption spectrum of the GdN shows a clear fundamental band edge of GdN around 800 nm; this transition is attributed to the minority spin band energy of GdN at the X point. Nitrogen vacancy centers cause a blue-shift of the optical band edge of GdN, which could be ascribed to both the band filling, and the electron-hole interactions resulting from the free carriers generated by nitrogen vacancies. Temperature-dependent magnetization measurements demonstrate a clear change in the magnetization values of GdN with respect to the N2 partial pressure. Nitrogen vacancy centers in the thin GdN film raise the Curie temperature from 31 K to 39 K, which has been accurately measured by the Arrott plots.

Fabrication of Visible-Light-Transparent Solar Cells Using p-Type NiO Films by Low Oxygen Fraction Reactive RF Sputtering Deposition

Visible-light-transparent p-type NiO films were deposited by reactive RF sputtering under unintentional heating. An optical transmittance of >80% was obtained in the wavelength range of 500–800 nm when the films were deposited under a very low O2 fraction in the gas phase O2/(Ar+ O2) = 0.5%. This result may reflect a decrease in the concentration of Ni vacancies due to the increase in their formation energy under oxygen-poor deposition conditions. Heterostructure pn junctions consisting of p-type NiO and n-type ZnO layers were also deposited. We eventually observed a slight but noticeable photovoltaic effect.

The effects of the pressure and the oxygen content of the sputtering gas on the structure and the properties of zinc oxy-nitride thin films deposited by reactive sputtering of zinc

Zinc nitride and oxy-nitride thin films were prepared by reactive magnetron rf sputtering of zinc in either nitrogen–argon or nitrogen–argon–oxygen ambient. The effects of varying the total sputtering pressure and the oxygen fraction in the total sputtering gas mixture on the microstructure, electrical and optical properties were investigated. With increasing the sputtering pressure, the dominant phase comprising the film material changes from the crystalline zinc nitride phase to crystalline zinc oxide. The characteristic pressure, at which this change in the dominant phase is observed, decreases with the increase of the oxygen fraction in the total sputtering gas mixture. The increase of the oxygen content in the films (from 5 at.% to a maximum of 40 at.%) and the downward shift in the optical absorption edge (from 920 to 400 nm), combined with the x-ray diffraction data, support these observations, indicating the controllable fabrication of an oxy-nitride film material. Correlations between the films’ fabrication conditions, including post-deposition annealing, their structure and composition, and their electrical properties are examined as well.

MoO3 back contact for CuInSe2-based thin film solar cells

ABSTRACTMoO3 films with a high work function (5.5 eV), high transparency, and a wide bandgap (3.0 - 3.4 eV) are a potential candidate for the primary back contact of Cu(InGa)Se2 thin film solar cells. This may be advantageous to form ohmic contact in superstrate devices where the back contact will be deposited after the Cu(InGa)Se2 layer and MoSe2 layer doesn’t form during Cu(InGa)Se2 deposition. In addition, the MoO3 may be incorporated in a transparent back contact in tandem or bifacial cells. In this study, MoO3 films for use as a back contact for Cu(In,Ga)Se2 thin film solar cells were prepared by reactive rf sputtering with O2/(O2+Ar) = 35%. The effect of post processing on the structural properties of the deposited films were investigated using x-ray diffraction and scanning electron microscopy. Annealing resulted in crystallization of the films to the α-MoO3 phases at 400°C. Increasing the oxygen partial pressure had no significant effect on optical transmittance of the films, and bandgaps in the range of 2.6-2.9 eV and 3.1-3.4 eV were obtained for the as deposited and annealed films, respectively. Cu(In,Ga)Se2 thin film solar cells prepared using an as-deposited Mo-MoO3 back contact yielded an efficiency of >14% with VOC = 647 (mV), JSC = 28.4 (mA), and FF. = 78.1%. Cells with ITO-MoO3 back contact showed an efficiency of ∼12% with VOC = 642 (mV), JSC = 26.8 (mA), and FF. = 69.2%. The efficiency of cells with an annealed MoO3 back contact was limited to 4%, showing a blocking diode behavior in the forward bias J-V curve. This may be caused by the presence of a barrier between the valence bands of the Cu(In,Ga)Se2 and MoO3, due to the higher bandgap of the annealed MoO3 films. SEM cross section studies showed uniform coverage of the as-deposited MoO3 layer and formation of voids for the annealed MoO3 film. Structural orientation of the Cu(In,Ga)Se2 absorber layer was also altered by the MoO3 film and less-oriented films were observed for either cases.

XRD Characterization of AlN Thin Films Prepared by Reactive RF-Sputter Deposition

AlN thin films have been grown on R((1-12) surface-cut)-Al2O3, SiO2-glass and C((001) surface-cut)-Al2O3 substrates, by using a reactive-RF-sputter-deposition method. X-ray diffraction (XRD) shows that AlN film has (110) orientation of wurtzite crystal structure for R-Al2O3 and (001) orientation for SiO2-glass and C-Al2O3 substrates. The film thickness was analyzed by Rutherford backscattering spectroscopy (RBS) and it appears that XRD intensity does not show a linear increase with the film thickness but a correlation with the stress, i.e., deviation of the lattice parameter of the film from that of bulk. The film composition and impurities have been analyzed by ion beam techniques. Effects of high-energy ion beams are briefly presented on atomic structure (whether stress relaxation occurs or not), surface morphology and optical properties.

Effect of electrode type in the resistive switching behaviour of TiO2 thin films

The influence of the electrode/active layer on the electric-field-induced resistance-switching phenomena of TiO2-based metal–oxide–metal devices (MOM) is studied. TiO2 active layers were fabricated by the reactive rf-sputtering technique and devices were made by sandwiching between several metal electrodes. Three different MOM devices were made, according with the junction type formed between the electrode and the TiO2 active layer, those where Ohmic–Ohmic, Ohmic–Schottky and Schottky–Schottky. The junction type was tested by electrical I–V measurements. It was found that MOM devices made with the Ohmic–Ohmic combination did not show any resistive switching behaviour in contrast with devices made with Ohmic–Schottky and Schottky–Schottky combinations. From a detailed analysis of the I–V curves it was found that transport characteristics are Ohmic for the low-resistance state for all the contacts combinations of the MOM devices, whereas in the high-resistance state it depends on contact combinations and can be identified as Ohmic, Schottky and Poole–Frenkel type. These conduction mechanisms in the low- and high-resistance states suggest that formation and rupture of conducting filaments through the film oxide is the mechanism responsible for the resistance switching.

High photo-responsivity ZnO UV detectors fabricated by RF reactive sputtering

High performance ultraviolet (UV) detectors based on ZnO metal–semiconductor–metal (MSM) and p–n heterojunctions, p-NiO/n-ZnO, were fabricated and their UV photo-responsivity was measured at room temperature. High-quality ZnO and NiO thin films were deposited on quartz substrates at room temperature under optimized RF reactive sputtering conditions. For ZnO-based MSM UV detectors using Al as a contact metal, the linear current–voltage (I–V) characteristics under a forward bias exhibited ohmic metal–semiconductor contact. A maximum photocurrent and photo-responsivity of 2.5mA and 1410A/W, respectively, at 365nm under 5V bias was observed, indicating the high photo-responsivity of the ZnO MSM detector. In comparison, a p-NiO/n-ZnO p–n heterojunction UV detector demonstrated clear rectifying I–V characteristics with an ideality factor, forward threshold voltage and photo-responsivity of 2, 0.9V and 0.09A/W, respectively, at 362nm under a reverse bias of 4V, which is close to that of the commercial GaN UV detector (∼0.1A/W).

Thin film high dielectric constant metal oxides prepared by reactive sputtering

High dielectric constant, low loss dielectric thin film materials produced by reactive RF sputtering have been investigated for use as capacitor dielectrics in integrated circuits, using oxides of niobium, tantalum, titanium, hafnium, and zirconium and mixtures of these with aluminum oxide. High breakdown fields and low leakage currents are found for the best materials and a reduction in capacitor area of a factor of >3 compared with Si3N4 capacitors of the same value, using a simple production process compatible with semiconductor device manufacturing.

스퍼터링에 의해 제조된 SnO 박막의 RF 파워에 따른 특성 연구

SnO thin films were fabricated by rf reactive sputtering on borosilicate substrates with an Sn target and Ar/O₂ gas mixture. The effect of rf power on the structural, electrical, and optical properties of SnO thin films was investigated with XRD, AFM, SEM, Hall effect measurements, and UV-Vis spectrometer. As a plasma power increased the crystallinity with a preferred orientation of SnO thin films was improved and the grain size slightly increased. However the grains were coalesced and excessively irregular in shape. The electrical conductivity of SnO thin films demonstrated a relatively low p-type conductivity of 0.024 (Wcm) ?1 at a higher power condition. Lastly, SnO thin films had poor optical transmittance in the visible range as a plasma power increased.

Effect of stirring on the properties of SILAR Cu-rich CuInS2films

CuInS2 (CIS) thin films are prepared by the successive ionic layer adsorption and reaction method (SILAR) by single cationic route under two different conditions (without stirring and with stirring). The effect of stirring on the structural, optical, compositional and morphological properties of the prepared Cu-rich CuInS2 thin films has been studied and reported in this paper. Full Text: PDF References M.Krunks, A.Mere, A.Katerski, V.Mikli and J.Krustok, "Characterization of sprayed CuInS2 films annealed in hydrogen sulfide atmosphere", Thin Solid Films 511-512, 434 (2006).CrossRef S.K.Kim, W.J.Jeong, G.C.Park, Y.G.Back, Y.G.Jeong and Y.T.Yoo, "Heat-treatment effect of chalcopyrite copper indium disulphide thin film growth", Synthetic Metals 71, 1747 (1995).CrossRef Roland Scheer, Progress in photovoltaics: Research and Applications, "Open questions after 20 years of CuInS2 research", (2012).CrossRef M.Krunks, O.Kijatkina, H.Renace, I.Oja, V.Mikli and A.Mere, "Composition of CuInS2 thin films prepared by spray pyrolysis", Thin Solid Films 403-404, 71 (2002).CrossRef Y.B.He, T.Kramer, I.Osterreicher, A.polity, R.Gregor, W. Krieg seis, D.Hasselkamp and B.K.Meyer, "Highly (112)-Oriented CuInS2 Thin Films Deposited by a One-Stage RF Reactive Sputtering Process", Jpn.J.Appl.Phys. 41, L484 (2002).CrossRef J.Qiu, Z.Jin, J.Qian, Y.Shi and W.Wu, "ILGAR CuInS2 films from various preparation conditions", Mater. Lett. 59, 2735 (2005).CrossRef N.Suriyanarayanan and C.Mahendran, "EDAX, SEM, Photoluminescence and Electrical properties of Zn- doped polycrystalline CuInS2 Thin films by spray pyrolysis", Archives of Physics Research 3 (1), 54 (2012).DirectLink Y.Pena, S.Lugo, M.C.Rodriguez, A.Vazquez, I.Gomez and P.Elizo nodo, "CuInS2 thin films obtained through the annealing of chemically deposited In2S3?CuS thin films", Appl.Surf. Sci. 257, 2193 (2011).CrossRef A.B.Mandale, S.D.Sathaye and K.R.Patil, "Preparation of Q-copper indium sulfide thin films by liquid?liquid interface reaction technique (LLIRT)", Mater. Lett. 55, 30 (2002).CrossRef M.Ben Rabeh, N.Chaglabou and M.Kanzari, "Effect of Antimony Incorporation in CuInS2 Thin Films", Chalcogenide Lett. 6 (4),155 (2009).CrossRef Y.B.He, A.Polity, R.Gregor, D.Pfisterer, I.Osterreicher, D.Hasse lkamp and B.K.Meyer, "Characterization of RF reactively sputtered Cu?In?S thin films", Physics B. 308-310, 1074 (2001).CrossRef K.Zeaiter, Y.Llinares and C.Llinares, "Structural and photoluminescence study of the quaternary alloys system CuIn(SxSe1?x)2", Sol. Energy Mater. Sol. Cells 61, 313 (2000).CrossRef A.Antony, A.S.Asha, R.Yoosuf, R.Manoj and M.K.Jayaraj, "Growth of CuInS2 thin films by sulphurisation of Cu?In alloys", Sol. Energy Mater. Sol. Cells 81, 407 (2004)CrossRef Y.Shi, Z.Jin, C.Li, H.An and J.Qiu, "Effect of [Cu]/[In] ratio on properties of CuInS2 thin films prepared by successive ionic layer absorption and reaction method", Appl. Surf. Sci. 252, 3737 (2006).CrossRef S.J.Roh, R.SMane, H.Pathan, O.S.Joo and S.H.Han, "Rapid growth of nanocrystalline CuInS2 thin films in alkaline medium at room temperature", Appl. Surf. Sci. 252, 1981 (2005).CrossRef Gray Hodes, Chemical Solution Deposition of Semiconductor Films (Marcel Dekker, Inc, pp-131).DirectLink R.P.Wijesundera and W.Siripala, "Preparation of CuInS2 thin films by electrodeposition and sulphurisation for applications in solar cells", Sol. Energy Mater. Sol. Cells 81, 147 (2004).CrossRef C.Guillen, J.Herrero, M.T.Gutierrez and F.Briones, "Structure, morphology and optical properties of CuInS2 thin films prepared by modulated flux deposition", Thin solid films 480- 481, 19 (2005). DirectLink P.Guha, S.Gorai, D.Ganguli and S.Chanudhuri, "Ammonia-mediated wet chemical synthesis of CuInS2"Mater. Lett. 57, 1786 (2003).CrossRef Y.B.He. T.Kramer, I.Osterreicher, A.Polity, B.K.Meyer and M.Hardt, "Post-growth treatment effects on properties of CuInS2 thin films deposited by RF reactive sputtering", Semicond. Sci.Technol. 20, 685 (2005).CrossRef S.Aksay and B.Altiokka, "Effect of substrate temperature on some of the optical parameters of CuInS2 films", Physica Status Solidi (c) 4, 585-588, No.2 (2007)CrossRef N.M.Ravindra, Preethi Ganapathy, Jinsoo Choi, "Energy gap?refractive index relations in semiconductors ? An overview", Infrared Physics and Technology, 50, 1 21 (2007)CrossRef

Fabrication and properties of nanocrystalline Zn‐Ir‐O thin films

AbstractNew p‐type semiconducting ZnIrSiO thin films were fabricated using reactive magnetron RF sputtering from ZnIrSi target. Their transport properties were: resistivity ρ=0.6 Ωcm, hole concentration p=5x1018 cm‐3 and mobility μ=2 cm2/Vs. Optical transmission in the visible wavelength region is 70% and band gap width Eg=3.17 eV. Films are XRD amorphous. HRTEM analysis revealed that ZnIrSiO films were composed of 1‐3 nm in diameter nanograins of Ir3Si and ZnIr2O4 embedded in an amorphous SiO2 matrix. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sputtered thin film piezoelectric aluminum nitride as a functional MEMS material

A comprehensive study on the complete process for the fabrication of AlN-based MEMS sensors and actuators is presented. Varying the bias voltage during the reactive rf sputtering enables to adjust the stress level in AlN films in the range of about 2 GPa. For the first time the influence of the rf bias power on the whole set of piezoelectric parameters was investigated. It could be shown that the dielectric permittivity, dielectric loss, rocking curve width, effective longitudinal piezoelectric coefficient d 33,f and effective transverse piezoelectric coefficient e 31,f remained unchanged. Further it was observed that piezoelectric AlN films could be deposited at low process temperatures of only 200 °C. Moreover an increase in the e 31,f coefficient with thicker films could be stated. Finally cone formation during wet etching was observed and revealed a formation of {01–12} planes which exhibit a slow etching rate. The c-textured growth of AlN starts directly at the Pt interface.

Zinc nitride films prepared by reactive RF magnetron sputtering of zinc in nitrogen containing atmosphere

Zinc nitride films were deposited on glass or silicon substrates by reactive magnetron RF sputtering of zinc in N2–Ar ambient. The deposition conditions were optimized in terms of substrate temperature and N2/Ar sputtering gas ratio, and representative films were then studied by structure, optical and spectroscopy techniques, and electrical measurements. Spectroscopic ellipsometry and spectrophotometry measurements revealed that the material has a direct band gap close to 1.26 eV. Hall effect and resistivity measurements indicated n-type conductivity with a very high carrier concentration of about1021 cm−3, mobility of up to 90 cm2 V−1 s−1, and resistivity of ∼10−3 Ω cm. X-ray photoelectron spectroscopy spectra clearly showed the existence of not only Zn–N bonding but also of a fraction of N–N bonding configurations, together with an oxidized surface. According to energy-dispersive x-ray spectroscopy analysis, the as-deposited films were almost stoichiometric and contained only a small fraction of oxygen.

InXGa1-XN films deposited by reactive RF-sputtering

The low temperature deposition of photoconductive InXGa1-XN films was carried out by simultaneous reactive rf- magnetron sputtering. In the films deposited using Ga and In targets, XRD peaks corresponding to wurtzite InXGa1-XN were observed. The optical band gap energy decreased from 3.27eV to 1.63eV with increasing the In composition ratio X=In/(Ga+In) from 0 to 0.58. The N composition ratio N/(Ga+In) and photosensitivity of the film with the optical band gap energy of 2.09eV were 0.68 and 1.89, respectively. In order to improve the photosensitivity, GaN and InN targets were used instead of Ga and In targets. The N/(Ga+In) and photosensitivity of the film with the optical band gap energy of 2.08eV deposited using GaN and InN targets were 0.86 and 252, respectively.

Oxidation Resistance and Self Hardening of CrAlN/BN Nanocomposite Coatings

CrAlN/BN nanocomposite coatings were deposited on mirror-polished silicon wafer and high-speed steel (HSS) substrates using reactive cosputtering, i.e., pulsed dc and rf sputtering of CrAl and h-BN targets, respectively. Further, the oxidation resistance of the obtained coatings was investigated. The CrAlN/BN coating exhibited superior oxidation resistance properties when compared with those of the CrAlN coatings; after annealing the sample at 800 °C in air for 1 h, the plastic hardness value of the CrAlN coatings decreased to 50% of the as-deposited hardness value; in contrast, the CrAlN/BN coatings exhibited self-hardening phenomena from 700 to 800 °C in the range of 5 to 30%. In particular, the CrAlN/18 vol% BN coatings showed an increase of approximately 30% in hardness values, and a maximum hardness value of approximately 50 GPa was reached after annealing the sample at 800 °C in air. The plastic hardness value hardly changed when the sample was annealed up to 800 °C in nitrogen and argon; this result was contrary to the result obtained for the sample that was annealed in air. The radiofrequency glow discharge optical emission spectroscopy (rf-GD-OES) analysis of the CrAlN/18 vol% BN coating annealed in air revealed that the coating has an oxide layer deposited on the surface to a depth of ~200 nm. Conventional transmission electron microscopy (TEM) observations of the same coating indicate that the columnar structure was disrupted by a thin layer (30–40 nm) of the coating annealed in air. The indentation hardness value of the annealed coating was measured using Ar ion sputtering before and after etching of the annealed surface. Subsequently, when the oxide layer was etched to a depth of 200 nm from the surface, the hardness value decreased from approximately 48 GPa to 43 GPa; this result was similar to the results obtained for the as-deposited coating.

Conductivity of LaAlO<sub>3</sub>/SrTiO<sub>3</sub> Interfaces Made by Sputter Deposition

There is much interest in interfaces between insulating oxides, such as SrTiO3 (STO) and LaAlO3 (LAO), where a two dimensional electron gas can form due to the so-called polar discontinuity. These interfaces are mostly fabricated by Pulsed Laser Deposition (PLD). We have investigated such interfaces by reactive RF sputtering in a high-pressure oxygen atmosphere. The films are smooth and crystalline. Transmission Electron Microscopy indicates that the interfaces are sharp and continuous while Electron Energy Loss Spectroscopy data indicate some slight intermixing. However, we find these interfaces to be non-conducting. It appears that the sputtered interface is not electronically reconstructed in the way reported for films grown by PLD, notwithstanding the good structural quality and composition of the films

STRUCTURE AND PHOTOLUMINESCENCE PROPERTIES OF SILICON OXYCARBIDE THIN FILMS DEPOSITED BY THE RF REACTIVE SPUTTERING

Silicon oxycarbide ( SiCO ) thin films were prepared by the RF reactive sputtering technique on n-type silicon substrates with the target of sintered silicon carbide ( SiC ), and high purity oxygen was used as the reactant gas. The as-deposited films were annealed at temperatures of 600°C, 800°C, and 1000°C under nitrogen ambient, respectively. The films were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and photoluminescence (PL) spectrophotometer. The results show that annealing temperature plays an important role in the structure and photoluminescence of the films. The temperature 600°C is the most favorable annealing temperature for SiO 2 crystallization and the formation of 6H- SiC crystal phase in the SiCO films. The intense PL peaks located at 375 nm and 470 nm are observed at room temperature. The origin of the PL was discussed.

Synthesis of Light Emitting Ge Nanocrystals by Reactive RF Sputtering

In this work we report the results of the synthesis, structural and optical characterization of SiO2/Ge/SiO2heterostructures by reactive RF sputtering. The SiO2films were grown by reactive sputtering employing a plasma mixture of oxygen and argon. The Ge layer was grown employing an Ar atmosphere. The samples were prepared on p-type Si (1 1 1) substrates by reactive sputtering. The effect of the partial pressure of oxygen on the electronic properties of the heterostructure is reported[1]. Structural characterization was carried out by grazing angle X-ray difraction. Surface roughness was quantified by atomic force microscopy. The presence of Ge nanocrystals (Ge-NCs) was evidenced by X-ray diffraction. The vibrational properties were studied by Raman spectroscopy. The Raman spectra showed modes associated to germanium indicating the formation of low dimensionality germanium particles embedded within a SiO2matrix. Photoluminescence emission is observed around ~1.7 eV and it is associated to the quantum confinement of carriers in Ge-NCs. Ohmic contacts were deposited using a van der Pauw geometry employing an a AuSb alloy for the contacts. Temperature dependent Hall (T-Hall) measurements were done between 35 K and 150 K, using the van der Pauw method. The results indicated low resistivity values that could be explained due to some variable range hopping conduction mechanism.

RF Sputtering법에 의한 산화주석 박막의 진공 열처리 효과

Tin oxide thin films were deposited by rf reactive sputtering and annealed at 400℃ for 1 h in vacuum. To minimize the influence such as reduction, oxidation, and doping on tin oxide thin films during annealing, a vacuum ambient annealing was adopted. The structural, optical, and electrical properties of tin oxide thin films were characterized by X-ray diffraction, atomic force microscope, UV-Vis spectrometer, and Hall effect measurements. After vacuum annealing, the grain size of all thin films was slightly increased and the roughness (R a ) was improved, however irregular and coalesced shapes were observed from the most of the films. These irregular and coalesced crystal shapes and the possible elimination of intrinsic defects might have caused a decrease in both carrier concentration and mobility, which degrades electrical conductivity.

Spectroscopic ellipsometry studies of reactively sputtered nitrogen-rich GaAsN films

Nitrogen-rich GaAsN thin films have been deposited at 500°C by reactive rf sputtering of GaAs target in argon–nitrogen atmosphere. The arsenic content of the films was varied by changing the nitrogen percentage in the sputtering atmosphere and the As/Ga ratio in the films was estimated by X-ray fluorescence measurements. Spectroscopic ellipsometry measurements have been carried out on these films and the measured ellispometric spectra were fitted with theoretical spectra generated by using suitable model sample structures. From the best fit parameters of the dispersion model, band-gap values and variation of refractive index and extinction coefficient as a function of wavelength have been obtained for films deposited with different percentages of nitrogen in the sputtering atmosphere. The films deposited with 12% to 100% nitrogen in the sputtering atmosphere, which are of hexagonal GaN, exhibit GaN-like optical properties, though effects due to excess arsenic in amorphous phase are seen in the films deposited with less than 40% nitrogen. The films deposited with 5% to 12% nitrogen in sputtering atmosphere are dominantly polycrystalline GaAsxN1−x (x≈0.01 to 0.08) and exhibit variations in optical parameters, which are consistent with their structure and composition. The films deposited with less than 5% nitrogen in sputtering atmosphere are arsenic-rich and amorphous.