Effect of HCl addition on the crystalline fraction in silicon thin films prepared by hot-wire chemical vapor deposition

In an effort to increase the crystalline fraction of silicon films directly deposited on a glass substrate by hot-wire chemical vapor deposition, the effect of HCl addition was studied. The silicon film was deposited on a glass substrate at 320 °C under a reactor pressure of 1333 Pa at the wire temperature of 1600 °C with 10%SiH₄–90%He at a fixed flow rate 100 standard cubic centimeter per minute (sccm) and HCl varied at 0, 10, 16 and 28 sccm. With increasing HCl, the crystalline fraction of silicon was increased as revealed by Raman spectra but the growth rate was decreased.     

Tantalum oxide film prepared by reactive magnetron sputtering deposition for all-solid-state electrochromic device

Inorganic-solid-state electrolyte tantalum oxide thin films were deposited by reactive DC magnetron sputtering to improve the leakage and deterioration of traditional liquid electrolytes in electrochromic devices. O₂ at 1–20 sccm flow rates was used to deposit the tantalum oxide films with various compositions and microstructures. The results indicate that the tantalum oxide thin films were amorphous, near-stoichiometric, porous with a loose fibrous structure, and highly transparent. The maximum charge capacity was obtained at an oxygen flow rate of 3 sccm and 50 W. The transmission change of the Ta₂O₅ film deposited on a WO₃/ITO/glass substrate between colored and bleached states at a wavelength of 550 nm was 56.7%. The all-solid-state electrochromic device was fabricated as a multilayer structure of glass/ITO/WO₃/Ta₂O₅/NiO_x/ITO/glass. The optical transmittance difference of the device increased with increasing applied voltage. The maximum change was 66.5% at an applied voltage of ± 5 V.     

Initial growth behaviors of GaN layers overgrown by HVPE on one-dimensional nanostructures

We developed a novel technique for obtaining a residual-strain-free GaN layer by the hydride vapor phase epitaxy (HVPE) method using one-dimensional nanostructures. The GaN layer was grown on a Si(1 1 1) substrate with a conventional AlN film and one-dimensional GaN nanostructures. The nanostructures were grown for 2 h with a HCl:NH₃ gas flow ratio of 1:50. The growth rate of nanoneedles at 600 °C and nanorods at 650 °C were 2.553 and 2.193 μm/h, respectively. The overgrown GaN layer was grown at 1050 °C for 5 and 10 min. We obtained a GaN layer of 1.833 μm thickness and c = 5.1849 Å. The morphology, crystalline structure, and optical characteristics of the GaN layer were examined by field emission scanning electron microscopy, X-ray diffraction, and photoluminescence.     

Growth of calcium carbonate crystal imitating stalagmite growth in nature

Calcite crystals were prepared by dropping a saturated calcium carbonate aqueous solution on a substrate. The calcite crystals were grown with a growth rate of approximately 0.7 μm/day under the condition of aqueous temperature of 2 °C, aqueous concentration of 0.006 mol/l, and substrate temperature of 40 °C. When the calcite substrate was used, calcite crystals were grown epitaxially. Na₂CO₃ and CaCl₂ aqueous solutions were dropped and reacted on the calcite crystal substrate with a CaCO₃ concentration of 0.06 mol/l, which is 10 times the saturated concentration at an aqueous temperature of 40 °C. Rhombohedral calcite was also deposited epitaxially with a growth rate of about 6.3 μm/day under this condition.     

Fabrication of LiCoO2 thin film cathodes by DC magnetron sputtering method

LiCoO₂ thin films were fabricated on Al substrate by direct current magnetron sputtering method. The effects of Ar/O₂ gas rates and annealing temperatures were investigated. Crystal structures and surface morphologies of the deposited films were investigated by X-ray diffraction, Raman scattering spectroscopy and field emission scanning electron microscopy. The as-deposited LiCoO₂ thin films exhibited amorphous structure. The crystallization starts at the annealing temperature over 400 °C. However, the annealed films have the partially disordered structure without completely ordered crystalline structure even at 600 °C annealing. The electrochemical properties of the LiCoO₂ films were investigated by the charge–discharge and cycle measurements. The 500 °C annealing film has the highest capacity retention rate of 78.2% at 100th cycles.     

Formation and characterization of Si5C3 type silicon carbide by carbon ion implantation with a MEVVA ion source

A Si₅C₃ type silicon carbon has been prepared via carbon ion implantation into silicon substrate using a MEVVA ion source. Carbon ions were implanted into silicon substrate at a fluence of 5 × 10¹⁷ ions/cm² and then the as-implanted samples were annealed at 1250 °C for 2 h. The thermal annealing produced a silicon carbide layer on the surface of silicon substrate. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirm the existence of Si₅C₃, rather than SiC. The results of Fourier transform infrared reflection (FTIR) and Raman spectroscopy analyses show that the Si–C vibration frequency in crystalline Si₅C₃ is slightly less than that in crystalline β-SiC.     

Anodic bonding of silicon onto glass by ion-cut technique and their characterization using high resolution X-ray diffraction studies

Anodic bonding of single crystal silicon wafer with glass and subsequent splitting of the silicon wafer is done by ion-cut technique that involves proton bombardment at desired energies at a dose level > 5 × 10¹⁶ cm^− 2 and then subjected to the bond pair for heat treatment at ∼ 550 °C. Details of the bonding and splitting processes have been discussed in the present study. The high resolution X-ray diffractometry studies have been performed and found that transferred single crystalline thin silicon layer has less crystalline perfection than the original wafer. It suggests that some improvement is still required in the ion-cut technique to improve the crystalline quality of the transferred layer before going to be used for the device applications.     

Deposition of B4C/BCN/c-BN multilayered thin films by r.f. magnetron sputtering

Thin films of cubic boron nitride (c-BN) and B₄C/BCN/c-BN multilayers, were deposited by r.f. (13.56 MHz) multi-target magnetron sputtering from high-purity (99.99%) h-BN and a (99.5%) B₄C targets, in an Ar (90%)/N₂ (10%) gas mixture. Films were deposited onto silicon substrates with (100) orientations at 300 °C, with r.f. power density near 7 W/cm². In order to obtain the highest fraction of the c-BN phase, an r.f. substrate bias voltage between − 100 and − 300 V was applied during the initial nucleation process and − 50 to − 100 V during the film growth. Additionally, B₄C and BCN films were deposited and analyzed individually. For their deposition, we varied the bias voltage of the B₄C films between − 50 and − 250 V, and for the BCN coatings, the nitrogen gas flow from 3% to 12%. A 300-nm-thick TiN buffer layer was first deposited to improve the adhesion of all samples. X-ray diffraction patterns revealed the presence of c-BN (111) and h-BN phases. FTIR spectroscopy measurements indicate the presence of a peak at 780 cm^− 1 referred to as “out-of-plane” h-BN vibration mode; another peak at 1100 cm^− 1 corresponds to the c-BN TO mode and the “in-plane” vibration mode of the h-BN at 1400 cm^− 1. BN films deposited at 300 °C at a pressure of 4.0 Pa and under − 150 V of nucleation r.f. bias, applied for 35 min, presented the highest c-BN fraction, near 85%. By using 32 layers, it was possible to deposit a 4.6-μm-thick c-BN film with adequate mechanical properties and good adhesion to the substrate.     

Effect of substrate temperature on the properties of pyrolytically deposited nitrogen-doped zinc oxide thin films

The effect of substrate temperature (T_s) on the properties of pyrolytically deposited nitrogen (N) doped zinc oxide (ZnO) thin films was investigated. The T_s was varied from 300 °C to 500 °C, with a step of 50 °C. The positive sign of Hall coefficient confirmed the p-type conductivity in the films deposited at 450 °C and 500 °C. X-ray diffraction studies confirmed the ZnO structure with a dominant peak from (1 0 0) crystal plane, irrespective of the variation in T_s. The presence of N in the ZnO structure was evidenced through X-ray photoelectron spectroscopy (XPS) analysis. The obtained high N concentration reveals that the 450 °C is the optimal T_s. Atomic force microscope (AFM) analysis showed that the surface roughness was increased with the increasing T_s until 400 °C but then decreased. It is found that the transmittance of the deposited films is increased with the increasing T_s. The optical band gap calculated from the absorption edge showed that the films deposited with T_s of 300 °C and 350 °C possess higher values than those deposited at higher T_s.     

Effect of cooling rate and Mg content on the Al–Si eutectic for Al–Si–Cu–Mg alloys

This study investigates and clarifies the qualitative and quantitative effects of Mg content and cooling rate (ranging from 0.5 to 4 °C/s), on the modification of the silicon eutectic structure and on the undercooling of the silicon eutectic growth temperature (ΔT_Si-eut) in the series of Al–Si–Cu–Mg alloys. The critical Mg content to produce a notable improvement in the silicon eutectic by 1.5 modification levels (regardless of the cooling rate) is 0.6 wt.% Mg. A similar increase in the modification level was also observed when the cooling rate was increased to a maximum of 4 °C/s, regardless of the Mg content. Measurements of the area and roundness of the silicon particles showed a good correlation with the modification level. The undercooling (ΔT_Si-eut) increased by up to ~ 23 °C at a relatively high Mg content and cooling rate and up to ~ 14 °C when the Mg content was increased from 0.4 to 0.6 wt.%.     

Effects of substrate parameters on structure and optical properties of ZnO thin films fabricated by pulsed laser deposition

Highly oriented zinc oxide thin films have been grown on quartz, Si (1 1 1) and sapphire substrates by pulsed laser deposition (PLD). The effect of temperature and substrate parameter on structural and optical properties of ZnO thin films has been characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), optical transmission spectra and PL spectra. The experimental results show that the best crystalline thin films grown on different substrate with hexagonal wurtzite structure were achieved at growth temperature 400–500 °C. The growth temperature of ZnO thin film deposited on Si (1 1 1) substrate is lower than that of sapphire and quartz. The band gaps are increasing from 3.2 to 3.31 eV for ZnO thin film fabricated on quartz substrate at growth temperature from 100 to 600 °C. The crystalline quality and UV emission of ZnO thin film grown on sapphire substrate are significantly higher than those of other ZnO thin films grown on different substrates.     

Photoluminescence properties of TiO2: Eu3 + thin films deposited on different substrates

Strong photoluminescence of Eu^3 + due to intra 4f transitions are obtained from amorphous xerogel TiO₂: Eu^3 + films prepared by sol–gel method and treated at a low temperature of 100 °C. The films are deposited on four different substrates: Si, Al, AAO (anodic alumina oxide) and porous silicon. We find that the luminescence intensity on AAO substrate increased 4 times comparing with that of Si or Al, and luminescence intensity decreases obviously on porous silicon substrate. Energy transfer mechanism from TiO₂ host to Eu^3 + is deduced through analysis of photoluminescence and photoluminescence excitation spectrum. Concentration quenching of Eu^3 + does not appear even at high atomic concentration of 7.69%.     

Fabrication and characterization of n-type aluminum-boron co-doped ZnO on p-type silicon (n-AZB/p-Si) heterojunction diodes

In this paper, the growth of n-type aluminum boron co-doped ZnO (n-AZB) on a p-type silicon (p-Si) substrate by sol–gel method using spin coating technique is reported. The n-AZB/p-Si heterojunctions were annealed at different temperatures ranging from 400 to 800 °C. The crystallite size of the AZB nanostructures was found to vary from 28 to 38 nm with the variation in annealing temperature. The band gap of the AZB decreased from 3.29 to 3.27 eV, with increasing annealing temperature from 400 to 700 °C and increased to 3.30 eV at 800 °C probably due to the formation of Zn₂SiO₄ at the interface. The band gap variation is explained in terms of annealing induced stress in the AZB. The n-AZB/p-Si heterojunction exhibited diode behavior. The best rectifying behavior was exhibited at 700 °C.     

Deposition of nanocrystalline ZnO by wire explosion technique and characterization of the films' properties

ZnO films deposited on glass, quartz and Al on silicon mono-crystal Si (100) substrates by using the wire explosion technique were investigated by X-ray diffraction (XRD), UV–VIS spectroscopy, scanning electron (SEM) and atomic force microscopy (AFM) measurements. X-ray diffraction measurements have shown that ZnO films are mainly composed of (100), (002) and (101) orientation crystallites. The post-deposition thermal treatment at 600 °C temperature in air has shown that the composite of Zn/ZnO film was fully oxidized to ZnO film. The XRD spectra of the film deposited in oxygen atmosphere at room temperature present high intensity dominating peak at 2h = 36, 32° corresponding to the (101) ZnO diffraction peak. The small fraction of the film (7%) corresponds to the (002) peak intensity at 2h = 34, 42°. This result indicates the good crystal quality of the film and hexagonal wurtzite-type structure deposited by zinc wire explosion. The optical absorption spectra shows the bands at 374, 373 and 371 nm corresponding to deposition conditions. The SEM analysis shows that ZnO films presented different morphologies from fractal network to porous films depending on deposition conditions. AFM analysis revealed the grain size ranges from 50 nm to 500 nm. The nanoneedles up to 300 nm in length were found as typical structures in the film. It was demonstrated that the wire explosion technique is a feasible method to produce ZnO crystalline thin films and nanostructures.     

Promotion of L10 ordering in Pt-rich nonepitaxially grown FePt films

Multilayer Fe/Pt films with atomic ratios Fe_xPt_100-x (x = 36 ~ 58) were deposited directly onto quartz glass substrates at room temperature through magnetron sputtering. Post-annealing from 300 °C to 600 °C was carried out to investigate the effect of varied compositions on the L1₀ ordering process. The result, which is different from that of co-sputtering growth, shows an obvious promotion of the phase transformation for slightly Pt-rich off-stoichiometric compositions with x between 40 and 50. The in-plane coercivity of Fe₄₈Pt₅₂ can reach 4.1 kOe even after annealing at 300 °C. This facilitated atomic diffusion and ordering might be related to the lattice expansion due to excessive Pt content.     

Shape memory behavior of Fe–Pd alloy thin films prepared by dc magnetron sputtering

Fe–Pd films have been deposited onto fused quartz and silicon substrates by dc magnetron sputtering. When an arc-melted and homogenized Fe–30at.% Pd alloy disk was used as a sputtering target, Fe–Pd films fabricated was shown to contain about 24 at.% Pd under the deposition condition used. The target configuration was then modified by placing Pd wires on the target so as to control the Pd content of films with an accuracy of 1 at.% Pd. Fe–Pd films containing 28.5 at.% Pd underwent a thermoelastic fcc-to-fct martensite transformation after annealing at 900 °C followed by quenching into iced water. Apparently, the reverse transformation was also thermoelastic and the thermoelastic transformations occurred repeatedly upon thermal cycling. Some of the Fe–28.5at.% Pd films were peeled off from the quartz substrate and they showed SM effects upon heating after deformation. A diaphragm-shaped free-standing film was also fabricated on a thin Si substrate. This film showed attractive transformation characteristics, including a narrow transformation hysteresis loop of about 4 °C and a small temperature difference between M_f and A_f (about 10 °C) in addition to M_s (43 °C) close to room temperature. This diaphragm-shaped film showed a reversible ballooning behavior with a maximum strain of about 0.05% upon thermal cycling.     

Spray pyrolysis deposition of lanthanum telluride thin films and their characterizations

Spray pyrolysis method is used to deposit lanthanum telluride (La₂Te₃) thin films on glass substrates. The films are deposited by pyrolysis of sprayed solutions of LaCl₃ and Te metal dissolved in concentrated HCl and HNO₃ along with hydrazine hydrate as a reducing agent. X-ray diffraction analyses show that the films are polycrystalline with La₂Te₃ phase. The films have a direct optical band gap of 2.2 eV. The films are p-type semiconductors with an electrical resistivity of the order of 10⁴ Ω cm at ambient temperature (27 °C).     

Photoluminescence properties of the Yb:Er co-doped Al2O3 thin film fabricated by microwave ECR plasma source enhanced RF magnetron sputtering

The Yb:Er co-doped Al₂O₃ thin film was deposited on oxidized silicon wafers by microwave ECR plasma source enhanced RF magnetron sputtering, and annealed from 800 °C to 1000 °C. The photoluminescence at 1.53 μm of thin film was obtained under room temperature. The mixture phase structure of γ and θ is observed by XRD, and the compositions of the thin film are investigated by EPMA. The maximum PL intensity was achieved with O₂:Ar at 1:1, annealing temperature at 900 °C, and experimental ratio of Yb:Er at 1:3.6. The energy transfer mechanism between Er and Yb ions is supported by theoretical analysis and experiment results.     

Ni–P amorphous phases obtained by Nd–YAG pulsed laser alloying of deposited Ni–P coating with aluminum

Ni–P electroless deposited coating with crystalline morphology was prepared on aluminum substrate. A Nd–YAG pulsed laser was used to alloy the materials at the condition of power density 5.36 × 10⁹ W/m² and scanning speed 3.0 mm/s. In the laser alloyed layer, Ni–P amorphous phases were found by means of TEM. Electron diffraction patterns and X-ray diffraction results showed that these Ni–P amorphous phases were decomposed as Ni and Ni₃P equilibrium phases when tempered at temperature over 300 °C.     

Studies on optical,chemical, and electrical properties of rapid SiO2 atomic layer deposition using tris(tert-butoxy)silanol and trimethyl-aluminum

Rapid SiO₂ atomic layer deposition (ALD) was used to deposit amorphous, transparent, and conformal SiO₂ films using tris(tert-butoxy)silanol (TBS) and trimethyl-aluminum (TMA) as silicon oxide source and catalytic agent, respectively. The growth rate of the SiO₂ films drastically increased to a maximum value (2.3 nm/cycle) at 200 °C and slightly decreased to 1.6 nm/cycle at 275 °C. The SiO₂ thin films have C–H species and hydrogen content (～8 at%) at 150 °C because the cross-linking rates of SiO₂ polymerization may reduce below 200 °C. There were no significant changes in the ratio of O/Si (～2.1) according to the growth temperatures. On the other hand, the film density slightly increased from 2.0 to 2.2 although the growth rate slightly decreased after 200 °C. The breakdown strength of SiO₂ also increases from 6.20 ± 0.82 to 7.42 ± 0.81 MV/cm. These values suggest that high cross-linking rate and film density may enhance the electrical property of rapid SiO₂ ALD films at higher growth temperature.