Narrow Results

Ba(Mg${}_{1∕3}$Nb${}_{2∕3})$O₃ (BMN) doped and undoped Ba${}_{0.45}$Sr${}_{0.55}$TiO₃ (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO₂/SiO₂/Al₂O₃ substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss ($\sim$38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg${}^{2+}$ whose detrimental effect on tunability is partially compensated by small Nb${}^{5+}$ as the two substitute Ti${}^{4+}$ in the BST. The coupling between ${\text{Mg}}_{\mathrm{\text{Ti}}}^{″}$ and V${}_{\mathrm{\text{O}}}^{••}$ charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions. The LC of the films was investigated in the temperature range of 300–450K. A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from ${\text{Mg}}_{\mathrm{\text{Ti}}}^{″}$, V${}_{\mathrm{\text{O}}}^{••}$ and Nb${}_{\mathrm{\text{Ti}}}^{•}$ charged defects. The carrier transport properties of the films were analyzed in light of Schottky thermionic emission (SE) and Poole–Frenkel (PF) emission mechanisms. The result indicated that while the carrier transport mechanism in the undoped film is interface limited (SE), the conduction in the BMN doped film was dominated by bulk processes (PF). The change of the conduction mechanism from SE to PF as a result of BMN doping is attributed to the presence of uncoupled Nb${}_{\mathrm{\text{Ti}}}^{•}$ sitting as a positive trap center at the shallow donor level of the BST.

In this study Al-doped Zinc Oxide (AZO) thin films were successfully deposited on the flexible Polymethyl methacrylate (PMMA) substrate by RF magnetron sputtering. The effects of RF power on the crystal structure, morphology, thickness and optical properties of AZO thin films have been investigated. The AZO thin films were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), DEKTAK 3 profilometer, UV–Visible spectroscopy and room temperature photoluminescence (PL) spectroscopy. The XRD patterns show that increase of RF power leads to increase in the predominant direction along (100) and crystal plane of hexagonal ZnO. Moreover, the transmittance of thin films decreased from 76% to 61% and optical bang gap varied among 3.34eV to 3.22eV with increasing RF power. The PL spectra show excellent light-emitting characteristics: 375nm, 428nm, 467nm and 505nm. The results indicate that the peak intensity increases with increasing RF power from 80W to 180W.

X-ray photoelectron spectroscopy (XPS) analysis of amorphous carbon (a-C)-based nanocomposite films has been carried out. Four bonding types of carbon are revealed from the C 1s spectra: C–Csp² and sp³ bonding, C–O and C–Ti bonding. With the introduction of Ti and Al into the a-C matrix, the carbon sp³/sp² ratio decreases significantly. XPS results also confirm that the Al doped in the film basically exists as an elemental Al in the a-C matrix, and the titanium is mostly bonded with carbon to form nc-TiC.

Silicon carbon nitride (SiCN) films were prepared on silicon substrate by reactive magnetron sputtering of a sintered silicon carbide target in a mixture of argon, nitrogen and acetylene. Detailed studies including energy dispersive spectrometer, atomic force microscope, X-ray diffraction, Fourier transformed infrared spectrometry and $C$–$V$ measuring instrument were performed. The as-deposited SiCN films do not exhibit obvious crystalline phase, and the SiCN films annealed at 600${}^{\circ }$C show SiC crystal and graphite carbon. The SiCN films mainly consist of Si–N, Si–C, Si–O, C–C, C$\equiv$N, Si–H_n and N–H_n bonds, and increasing C₂H₂ flow rate promotes the formation of C–C, N–H_n and Si–N bonds. The SiCN film with low dielectric constant of 3.8 and compact structure was successfully prepared.

SnSe is a potential thermoelectric material, but there are few reports about the thermoelectric properties of the film. In this work, SnSe thin films were deposited on glass substrates by RF magnetron sputtering from SnSe alloy target. The effect of substrate temperature on the structural and thermoelectric properties was investigated. It was found that the columnar grains and the surface roughness of the films increase with increasing the substrate temperature. The film deposited at 558 K exhibited a high crystalline quality and stoichiometric composition, which has a maximum power factor of 1.4uWcm${}^{-1}$K${}^{-2}$ at 575K. The results of this work demonstrate the importance of high substrate temperature to obtain high thermoelectric performance SnSe films.

The influence of mild thermal annealing and nickel addition on the magnetic properties of Co–CoO multilayers is investigated. Co–CoO and CoNi–CoNiO multilayers were fabricated by radio-frequency magnetron sputtering and natural oxidation. Their magnetic properties have been studied via the magneto-optical Kerr effect and a vector network analyzer ferromagnetic resonance setup. The Co–CoO multilayers were annealed up to 90min at $250^{°}$C and they were found to be always in-plane magnetized. The value of Gilbert damping was evaluated. The multilayers after annealing or Ni addition show a small increase in coercivity without considerable changes in their anisotropy. The phenomenon of inverted hysteresis with negative remanence, with the field being applied perpendicular to the film plane, has been recorded. It was modeled with two coexisting magnetic moments with in-plane and perpendicular anisotropies, respectively.

We report the experimental observations of large spatially disk-shaped patterns in an iron (Fe) film system deposited on silicone oil surfaces by a DC-magnetron sputtering method. These disk patterns form spontaneously during deposition and grow successively in vacuum condition after deposition. Their nucleation, growth and evolution are strongly dependent on the sputtering power, deposition period and growth time. The experiment indicates that they may result from the spontaneous organization and gathering of the Fe atoms and atomic clusters driven by the internal stress.

During the sputtering-deposition process, the temperature of film growth surface is more important than that of the substrate, which could seriously influence the film growth behavior. While, it is difficult to measure the temperature of film growth surface, because of the low space resolution of traditional temperature measurement systems. In this paper, the temperature of TiO₂ film growth surface and substrate were monitored by the home-made NiCr/NiSi film thermocouple and standard NiCr/NiSi K type wire thermocouple. With the same sputtering parameters, the temperature of TiO₂ film growth surface could reach $846.2\pm 3.9^{\circ }$C. While, the temperature of substrate was only about $305.8\pm 1.4^{\circ }$C. Finally, combining the temperature of film growth surface in sputtering-deposition process, the film growth behavior can be investigated and controlled in future.

In this paper, Cu thin films were successfully deposited on glass substrates using DC magnetron sputtering at varying deposition times. The deposition time was varied as 5, 9, 11 and 17min. The obtained Cu thin films were analyzed for morphology and topography using atomic force microscopy (AFM). The size of the surface structures/grains was seen to evolve with deposition time. The conventional/statistical, fractal and multifractal analyses were carried out on AFM images using existing imaging algorithms. The arithmetic roughness and interface width parameters were seen to evolve with the sputtering time. The autocorrelation and height–height correlation functions revealed that the surfaces of all the Cu thin films exhibited self-affine character, but were not mounded properties. The fractal dimensions computed using box counting and power spectral density functions revealed that larger dimensions were associated with larger surface features. The lacunarity coefficients were too small indicating that the surfaces were generally deficient in porosity and other defects. The multifractal analyses revealed that spatial roughness does not exhibit linear relationship with the deposition time. The study reveals that surface evolution and nanoscale behavior is significantly influenced by the deposition time although a linear relationship is not established.

In this study, we show that by applying appropriate deposition conditions, Zn nanostructured templates for the growth of zinc oxide (ZnO) nanowires can be fabricated, from which ultrafine high optical quality nanowires can be grown by means of post-deposition low-temperature oxidation. By identifying and optimizing the appropriate parameters, we successfully fabricated long ultrafine ZnO nanowires up to 30 microns in length and 50 nm in diameter. Our report contradicts the commonly held paradigm that sputter deposition can only be used to fabricate thin films with no significant nanostructure morphology and provides a low cost, high throughput method of fabricating different ZnO nanostructures. The studies of photoluminescence (PL) of the nanowires showed their high optical quality with band edge dominated emission with small defect-related input.

InSb-based devices embedded in the human body can be utilized for biological applications, including the detection of biomagnetic fields owing to the high electron mobility of InSb, which is a suitable magnetic resistance element. In this study, the aqueous stability of In${}_{0.57}$Sb${}_{0.43}$/quartz prepared by RF magnetron sputtering was evaluated as the initial stage for use in biomedical devices. In${}_{0.57}$Sb${}_{0.43}$/quartz was coated with (3-mercaptopropyl) trimethoxysilane (MPT), as InSb was not stable under aqueous conditions. MPT coating did not affect the thin-film properties (such as surface morphology, crystal structure, and electrical properties) of In${}_{0.57}$Sb${}_{0.43}$/quartz. A cell viability assay confirmed the lower cytotoxicity of MPT-coated In${}_{0.57}$Sb${}_{0.43}$/quartz than that of bare In${}_{0.57}$Sb${}_{0.43}$/quartz because the MPT coating reduces the elution of indium from In${}_{0.57}$Sb${}_{0.43}$/quartz. In addition, the MPT coating essentially suppressed the deterioration of the thin-film properties under simulated physiological conditions. Therefore, MPT-coated InSb thin films are expected for use in temporary implanted biomedical devices.

Hydrogenated amorphous SiC films (a-Si_1-xC_x:H) were prepared by DC magnetron sputtering technique on p type Si(100) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6H-SiC). The deposited film a-Si_1-xC_x:H was realized under a mixture of argon and hydrogen gases. The (a-Si_1-xC_x:H) films have been investigated by scanning electronic microscopy equipped with EDS system (SEM-EDS), X-rays diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV-visible-IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure of a-Si_0.81C_0.19:H corresponding to 19 at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centered at 463 nm (2.68 eV) and 542 nm (2.29 eV). The structural properties and the origin of the luminescence were discussed.

Indium tin oxide (ITO) is widely used in the optoelectronic industry as a transparent conductive oxide owing to its excellent optical and electrical properties. To improve the physical properties of ITO, highly conductive ITO/Ag/ITO multilayer electrodes were prepared using radio frequency (RF) magnetron sputtering at room temperature. Then, laser annealing was performed on the multilayer electrodes with scanning intervals of 0.01, 0.02, 0.05 and 0.1 mm. The structural properties of the multilayer electrodes were characterized by X-ray diffraction, and their optical and electrical properties were characterized by ultraviolet (UV) visible spectrophotometry and a four-point probe station, respectively. The results demonstrated that the multilayer films had a polycrystalline structure, and ITO (222) and Ag (111) preferred orientations were identified after laser annealing. In addition, the crystalline size of the Ag layers increased slightly, implying that the defect density within the Ag layers was reduced, resulting in a significant increase in its conductivity. A significantly low electrical resistivity of 5.35 $\mathrm{\Omega }$/sq and high optical transmittance of 85% were achieved. The Haacke index value was ${\varphi }_{\mathrm{\text{Vis}}}\cong 37.74\times 10^{-3}{\mathrm{\Omega }}^{-1}$, which was much better than the value of ${\varphi }_{\mathrm{\text{Vis}}}\cong 18.14\times 10^{-3}{\mathrm{\Omega }}^{-1}$ before laser annealing.

A characteristic wedge-shaped iron (Fe) film system, deposited on glass substrate by a DC-magnetron sputtering method and quenched by silicone oil during deposition, has been successfully fabricated. The mechanical behaviors of the quenched and non-quenched Fe films have been compared and analyzed. The internal stress is found to transform from tension to compression in nature after quenching, which results in the formation of buckling pattern in the quenched Fe film while crack pattern in the non-quenched film. It is proposed that the origin of the compressive stress is mainly due to freezing of the Fe atoms (or clusters) with high kinetic energy and doping of the oil molecules into the Fe film defects.

InN film with an AlInN/AlN bilayer buffer was deposited on Si(111) substrate by radio frequency (RF) magnetron sputtering. X-ray diffraction and Raman spectroscopy measurements reveal that the InN film is of hexagonal wurtzite crystal structure with highly (0002) preferred orientation. An Al_0.24In_0.76N interface layer of about ~50 nm was confirmed by transmission electron microscopy (TEM) and further analyzed by X-ray photoelectron spectroscopy (XPS). The quality of this film is remarkably better than InN films grown directly on Si substrate or with only an AlN buffer, due to the effective accommodation of mismatch between the film and substrate. Our results will be very useful in the fabrication of applicable nitride microelectronic materials.

HfN and VN thin films were deposited onto silicon and 4140 steel substrates with r.f. reactive magnetron sputtering by using Hf and V metallic targets with 4-inch diameter and 99.9% purity in argon/nitrogen atmosphere, applying a substrate temperature of 250°C and a pressure of 1.2 × 10^-3 mbar. In order to evaluate the structural, chemical, morphological, mechanical and tribological properties, we used X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), scanning electron microscopy (SEM), nanoindentation, pin-on-disc and scratch tests. Film structure determined by XRD showed that FCC (NaCl-type) films are formed in both the cases by δ-HfN and δ-VN phases. Hardness and elastic modulus values obtained for both the films were 21 and 224 GPa for the HfN film and 19 and 205 GPa for the VN film, respectively. Additionally, the films showed low friction coefficient of 0.44 for HfN and 0.62 for VN when these films were evaluated against 100 Cr6 steel, and finally the critical load was found at 41 N for the HfN film and 34 N for the VN film.

Molybdenum thin films were sputter deposited under different conditions of DC power and chamber pressure. The structure and topography of the films were investigated using AFM, SEM and XRD techniques. Van der Pauw method and tape test were employed to determine electrical resistivity and interfacial strength to the substrate, respectively. All the films are of sub-micron thickness with maximum growth rate of 78 nm/min and crystallite size in the range of 4 to 21 nm. The films produced at high power and low pressure exhibit compressive residual strains, low electrical resistivity and poor adhesion to the glass substrate, whereas the converse is true for films produced at high pressure.

Ta (3.3 nm)/Ni–Al (3.3 nm) integrated films deposited on Si substrates by magnetron sputtering, annealed at various temperatures in a ultra-high vacuum, have been studied as diffusion barrier layers between Cu and Si for application in Cu interconnection. The images of transmission electron microscopy (TEM) prove that the cross-sectional interfaces of Cu/Ta/Ni–Al/Si sample annealed at 600°C are clear and sharp. No Cu–silicide peaks can be found from the X-ray diffraction (XRD) patterns of the 850°C annealed sample, but the sheet resistance of the sample increases abruptly. Moreover, large grooves are found from the image of atomic force microscopy (AFM) for the 850°C annealed sample, implying the failure of the diffusion barrier. The integrated Ta/Ni–Al barrier layer retains thermally stable nature up to at least 800°C, indicating that the Ta/Ni–Al integrated film is an excellent diffusion barrier between Cu and Si.

This paper presents the growth of bismuth ferrite (Bi₂Fe₄O₉) thin film by radio frequency magnetron reactive sputtering on p-Si (100) substrate and the characterization of the grown thin film. The deposited thin film is characterized by X-ray diffraction (XRD), field emission scanning electron micrograph (FESEM), energy dispersive X-ray analysis (EDAX), dielectric measurements and vibrating sample magnetometer (VSM) analysis. The XRD study reveals the orthorhombic structure of the crystallites and the particle size is calculated as 45 nm. The FESEM result confirms that the film has smooth surface and uniform distribution of nanoclusters. The percentage of chemical compositions of the film is confirmed by EDAX measurement. The dielectric behavior of the film is examined in terms of the dielectric constant and the dielectric loss as a function of frequency. The magnetic behavior of the film is measured using VSM with the applied magnetic field of about 1 Tesla and the result shows the ferromagnetic behavior of the sample at room temperature.

Zinc oxide (ZnO) thin films have been deposited onto thoroughly cleaned stainless steel (AISI SS 304) substrates by reactive direct current (dc) magnetron sputtering and the films were doped with silver (Ag). The prepared thin films were analyzed using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) to investigate the structural and morphological properties. The thickness values of the films were in the range of 194 to 256nm. XRD results revealed that the films were crystalline with preferred (002) orientation. Grain size values of pure ZnO films were found to be 19.82–23.72nm. On introducing Ag into ZnO film, the micro-structural properties varied. Adhesion test was carried out with Staphylococcus aureus (S. aureus) in order to know the adherence property of the deposited films. Colony formation units (CFU) were counted manually and bacterial adhesion inhibition (BAI) was calculated. We observed a decrease in the CFU on doping Ag in the ZnO films. BAI of the film deposited at – 100 V substrate bias was found to be increased on Ag doping from 69 to 88%.