Influence of rapid thermal annealing effect on electrical and structural properties of Pd/Ru Schottky contacts to n-type GaN

Pd/Ru metallization scheme is fabricated on n-GaN as a Schottky contact, and the electrical and structural properties have been investigated as a function of annealing temperature by current–voltage (I–V), capacitance–voltage (C–V), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. As-deposited Ru/Pd/n-GaN contact yielded Schottky barrier height (SBH) of 0.67 eV (I–V) and 0.79 eV (C–V), respectively. Further, it is observed that the Schottky barrier height increases to 0.80 eV (I–V) and 0.96 eV (C–V) for the contact annealed at 300 °C. However, both I–V and C–V measurements indicate that the barrier height slightly decreased when the contacts are annealed at 400 °C and 500 °C. From the above observations, the optimum annealing temperature for Pd/Ru Schottky contact is 300 °C. Norde method is also employed to extract the barrier height of Pd/Ru Schottky contacts which are in good agreement with those obtained by the I–V technique. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 300 °C compared to the as-deposited contact. Based on the XPS and XRD results, the reason for the increase in SBH upon annealing at 300 °C could be attributed to the formation of gallide phases at the Ru/Pd/n-GaN interface vicinity. The AFM results showed that the overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. The above observations reveal that the Pd/Ru Schottky contact is attractive for high-temperature device applications.     

Effects of annealing on optical and electrical characteristics of p-type semiconductor copper (II) oxide electrodeposits

The 1.35-eV-bandgap energy-CuO film with the optical absorption coefficient of 2.2 × 10⁴ cm^− 1 has been prepared on a conductive glass substrate by anodic electrodeposition in an aqueous solution containing copper (II) nitrate and ammonium nitrate at 298 K followed by annealing at 573 K and above in air. The as-deposited CuO film with a monoclinic lattice showed p-type conduction with resistivity of 2.2 × 10⁵ Ω cm and slightly expanded bandgap energy of 1.46 eV with the absorption coefficient of 1.3 × 10⁴ cm^− 1. The annealing induced changes in the grain morphology, bandgap energy, absorption coefficient, and resistivity, and the resistivity of 3.3 Ω cm could be obtained by annealing at 773 K.     

Structural and electrical properties of sputtered indium-zinc oxide thin films

In this study, indium-zinc oxide (IZO) thin films have been prepared at a room temperature, 200 and 300 °C by radio frequency magnetron sputtering from a In₂O₃-12 wt.% ZnO sintered ceramic target, and their dependence of electrical and structural properties on the oxygen content in sputter gas, the substrate temperature and the post-heat treatment was investigated. X-ray diffraction measurements showed that amorphous IZO films were formed at room temperature (RT) regardless of oxygen content in sputter gas, and micro-crystalline and In₂O₃-oriented crystalline films were obtained at 200 and 300 °C, respectively. From the analysis on the electrical and the structural properties of annealed IZO films under Ar atmosphere at 200, 300, 400 and 500 °C, it was shown that oxygen content in sputter gas is a critical parameter that determines the local structure of amorphous IZO film, stability of amorphous phase as well as its eventual crystalline structure, which again decide the electrical properties of the IZO films. As-prepared amorphous IZO film deposited at RT gave specific resistivity as low as 4.48 × 10^− 4 Ω cm, and the highest mobility value amounting to 47 cm²/V s was obtained from amorphous IZO film which was deposited in 0.5% oxygen content in sputter gas and subsequently annealed at 400 °C in Ar atmosphere.     

Changes in electrical and structural properties of indium oxide thin films through post-deposition annealing

The annealing effects on the electrical properties and microstructures of indium oxide (In₂O₃) thin films were investigated. The In₂O₃ thin films with the thickness of about 150 nm were annealed at various temperatures ranging from 100 to 600 °C in air after the sputtering deposition. It was found that the carrier density of the In₂O₃ thin films decreased with increasing in the annealing temperature and then started to increase at a certain temperature. This indicated that the reduction of the In₂O₃ thin films was promoted at high annealing temperature. The Hall mobility of the In₂O₃ thin films increased through the reduction; furthermore, the d-spacing of the In₂O₃ crystal lattice plane tended toward ideal value. It can be believed from these results that one of the principal electron scattering in the In₂O₃ thin films is attributed to excess oxygen atoms that expand the d-spacing.     

Effect of base and oxygen partial pressures on the electrical and optical properties of indium molybdenum oxide thin films

Indium molybdenum oxide thin films were RF sputtered at room temperature on glass substrates with a reference base pressure of 7.5 × 10^− 4 Pa. The electrical and optical properties of the films were studied as a function of oxygen partial pressures (OPP) ranging from 1.5 × 10^− 3 Pa to 3.5 × 10^− 3 Pa. The obtained data show that the bulk resistivity of the films increased by about 4 orders of magnitude (from 7.9 × 10^− 3 to 7.6 × 10¹ Ω-cm) when the OPP increased from 1.5 × 10⁻³ to 3.5 × 10^− 3 Pa, and the carrier concentration decreased by about 4 orders (from 1.77 × 10²⁰ to 2.31 × 10¹⁶ cm^− 3). On the other hand, the average visible transmittance of 30.54% of the films (brown colour; OPP = 1.5 × 10^− 3 Pa) was increased with increasing OPP to a maximum of 80.47% (OPP = 3.5 × 10^− 3 Pa). The optical band gap calculated from the absorption edge of the transmittance spectra ranges from 3.77 to 3.88 eV. Further, the optical and electrical properties of the films differ from those deposited at similar conditions but with a base pressure lower than 7.5 × 10^− 4 Pa.     

Cupric oxide inclusions in cuprous oxide crystals grown by the floating zone method

Abstract

Phase-pure cuprous oxide (Cu₂O) crystals are difficult to grow since cupric oxide can form within the crystal as the crystal is cooled to ambient conditions. Vacancies are the solute which causes precipitation of macroscopic defects. Therefore, even when a mostly phase-pure single crystal is used as a feed rod, cupric oxide inclusions persist in the recrystallized solid. Control of the thermal profile during crystal growth, however, can improve phase-purity; a slow counter-rotation rate of the feed and seed rods results in fewer inclusions. Cupric oxide can be removed by annealing, which produces a factor of 540 ± 70 increase in phase-purity.     

The effect of rapid thermal annealing on structural and electrical properties of TiB2 thin films

This work reports on the effect of post-deposition rapid thermal annealing on the structural and electrical properties of deposited TiB₂ thin films. The TiB₂ thin films, thicknesses from 9 to 450 nm, were deposited by e-beam evaporation on high resistivity and thermally oxidized silicon wafers. The resistivity of as-deposited films varied from 1820 μΩ cm for the thinnest film to 267 μΩ cm for thicknesses greater than 100 nm. In the thickness range from 100 to 450 nm, the resistivity of TiB₂ films has a constant value of 267 μΩ cm.

A rapid thermal annealing (RTA) technique has been used to reduce the resistivity of deposited films. During vacuum annealing at 7 × 10⁻³ Pa, the film resistivity decreases from 267 μΩ cm at 200 °C to 16 μΩ cm at 1200 °C. Heating cycles during RTA were a sequence of 10 s. According to scanning tunneling microscopy analysis, the decrease in resistivity may be attributed to a grain growth through polycrystalline recrystallization, as well as to an increase in film density.

The grain size and mean surface roughness of annealed films increase with annealing temperature. At the same time, the conductivity of the annealed samples increases linearly with grain size. The obtained results show that RTA technique has a great potential for low resistivity TiB₂ formation.     

溶剂热法制备不同微米结构的氧化亚铜

以乙酸铜为原料,采用溶剂热法合成了球形直径约为2~3μm和八面体粒径大小约为4μm的氧化亚铜颗粒。通过选用不同的还原剂如三乙醇胺和乙二醇,系统研究了不同反应体系中如反应温度、溶剂、原料配比和添加表面活性剂十六烷基三甲基溴化铵(CTAB)对微米结构氧化亚铜晶型与形貌的影响,选出制备氧化亚铜八面体和球形的最佳条件,并初步探讨了氧化亚铜微米颗粒的生长机理。     

The effect of high-temperature annealing on the structure and electrical properties of well-aligned carbon nanotubes

Systematic work has been performed on the effect of high-temperature annealing on structural defects and impurities of well-aligned carbon nanotubes (ACNTs) in this paper. ACNTs had been prepared by CVD process with ferrocene as catalyst and then the as-grown samples were experienced heat treatment (HT) from 1800 to 3000 °C. X-ray diffraction, Raman spectroscopy and electron dispersive spectroscopy (EDS), etc., have been used to analyze the effect of annealing. Results indicate that some impurities can be removed once annealing temperature exceeds vaporization point of corresponding metal or non-metal. Desorption of O should be attributed to reduced active sites of dangling covalent bonds after heat treatment. Specious discrepancy about interlayer spacing resulted from XRD and Raman tests show that although high-temperature heat treatment can remove in-plane defects of carbon nanotubes greatly, interlayer spacing between graphene shells could not be reduced effectively because of the special concentric cylindrical structure of nanotubes. Electrical resistivity of ACNTs block is about three orders higher than that of copper even after HT at 3000 °C, and the anisotropy of electrical properties increased once experienced heat treatment at increased temperature.     

Effect of samarium addition and annealing on the properties of electrodeposited ceria thin films

Samarium (Sm)-doped ceria (CeO₂) (SDC) is a promising material for high temperature electrochemical devices. Our work demonstrates that thin SDC films can be prepared by a cost-effective electrodeposition method at a low-temperature (30 °C) and − 0.8 V/SCE (saturated calomel electrode) potential. Analysis of the structural properties of the obtained SDC films, as-grown and annealed at 600 °C, has been carried out by X-ray diffraction (XRD). Morphology and film composition were studied using scanning electronic microscopy and energy dispersive X-ray analysis. Vibrational properties were determined by Raman spectroscopy. The effects of samarium addition into the deposition bath on the final film composition have been studied. According to XRD results, film crystallographic properties are directly linked to the percentage of Sm incorporated in the CeO₂ lattice. We report on the electrochemical deposition of the SDC films performed over a large range of Sm additions (0-30%). The effect of temperature annealing has been studied as well.     

The effect of deposition parameters and post treatment on the electrical properties of Mo thin films

In this study, we deposited low-resistivity molybdenum (Mo) thin films on soda-lime glass substrates with good adhesion. We adjusted various deposition parameters such as the sputtering power (52-102 W), working distance (5.5-9 cm) and annealing temperature (26-400 °C) to investigate their impact on the sheet resistance. By using a DC magnetron sputtering system, we obtained Mo thin films having the lowest sheet resistance of 0.190 Ω/□ with a sputtering power of 82 W, working distance of 6.5 cm, and annealing temperature of 400 °C; in addition, these films had good adhesivity. These Mo thin films were suitable for use as the Mo back contact in Cu(In,Ga)Se₂-based solar cells.     

A simple single-step approach towards synthesis of nanofluids containing cuboctahedral cuprous oxide particles using glucose reduction

Enhancement of thermal properties of conventional heat transfer fluids has become one of the important technical challenges. Since nanofluids offer a promising help in this regard, development of simpler and hassle free routes for their synthesis is of utmost importance. Synthesis of nanofluids using a hassle free route with greener chemicals has been reported. The single-step chemical approach reported here overcomes the drawbacks of the two-step procedures in the synthesis of nanofluids. The resulting Newtonian nanofluids prepared contained cuboctahedral particles of cuprous oxide and exhibited a thermal conductivity of 2.852 W·m^-1·K^-1. Polyvinylpyrrolidone (PVP) used during the synthesis acted as a stabilizing agent rendering the nanofluid a stability of 9 weeks.     

Morphology and growth of electrodeposited cuprous oxide under different values of direct current density

The growth of Cu₂O thin films electrodeposited by a two-electrode system with acid and alkaline electrolytes under different values of direct current (DC) densities was investigated. The microstructure of Cu₂O thin films produced in the acid electrolyte changes from a ring shape to a cubic shape with increasing DC density, and the microstructure of Cu₂O thin films produced in the alkaline electrolyte has a typical pyramid shape. The X-ray diffraction results show that Cu₂O thin films can be electrodeposited over a larger current domain than those deposited by a three-electrode system. The growth of Cu₂O thin films is examined under this domain, and the electrocrystallization process of such films is discussed taking into consideration the effect of current density on nucleation, cluster growth, and crystal growth.     

A comparative study of the effect of annealing and plasma treatments on the microstructure and properties of colloidal indium tin oxide films and cold-sputtered indium tin oxide films

Indium tin oxide (ITO) films were fabricated by (i) RF sputtering and (ii) spin coating of a colloidal ITO dispersion synthesized in-house. Films were deposited onto glass and quartz substrates and were annealed in air and in argon. The electrical properties of the films were studied as a function of annealing temperature and atmosphere. For the colloidal films, the effect of pre-annealing plasma treatments was also evaluated. Removal of the organic ligands from the colloidal films, in combination with annealing, resulted in over 8 orders of magnitude decrease in the film resistivity. It was found that plasma treatments were particularly effective in reducing film resistivity for low temperature annealed colloidal films. Results for the cold-sputtered films were for the most part as expected, with argon annealing resulting in lower resistivities than films annealed in air.     

A gradual annealing of amorphous sputtered indium tin oxide: Crystalline structure and electrical characteristics

Thin films of amorphous indium tin oxide were deposited by soft sputtering. The film was gradually annealed in air at temperatures from 110 °C to 150 °C. Its structural and electrical properties were monitored in order to get a better understanding of the annealing process. Firstly, carrier density decreases by oxygen intake. Crystallization speeds up at 150 °C, with a 2.5 D growth of crystallites. The preferred orientations come from sputtering induced seeds. Then, the carrier density increases again due to tin activation. Meanwhile, the carrier mobility is more damaged by the low temperature annealing in air than by a standard annealing in a reducing atmosphere. Thus, tin oxide segregation is suspected at grain boundaries.     

Effect of indium annealing on the electrical properties of polycrystalline n-type CdTe

Polycrystalline n-type CdTe samples were annealed in molten indium at 800°C for different times (150 to 350 h). D.c. conductivity () and Hall coefficient (R_H) studies were made on these samples in the temperature range 77 to 400 K. R_H and data were analysed based on the various models existing for polycrystalline semiconductors. The temperature variation of mobility data were analysed in the light of various scattering mechanisms; the role of grain-boundary scattering being examined in particular detail.     

Structure and photoconductive properties of dip-deposited SnS and SnS2 thin films and their conversion to tin dioxide by annealing in air

SnS and SnS₂ thin films have been prepared by the dip technique. In this technique, a substrate was dipped into an alcoholic solution of the corresponding chloride and thiourea and then withdrawn vertically at a controlled speed, and finally baked in a high temperature furnace at atmospheric condition. XRD and SEM data suggest that good quality SnS and SnS₂ films are obtained at a baking temperature of 300 and 360°C, respectively. Values of band gap for SnS and SnS₂ obtained from spectral response of photoconductivity are 1.4 and 2.4 eV, respectively. The indirect allowed band gap values for SnS₂ film obtained from optical absorption measurements are 1.95 and 2.05 eV. Open-air annealing of both SnS and SnS₂ films at 400°C converts them to transparent conducting SnO₂.     

Study of the conduction properties of silicon-rich oxide under illumination

Carrier transport in silicon-rich oxide (SRO) was studied under illumination using the standard current versus voltage and capacitance versus voltage measurements. Al/SRO/Si metal-oxide-semiconductor (MOS)-like structures were used, and SRO layers with different thickness and excess Si concentration were deposited by low-pressure chemical vapor deposition (CVD) technique. In reverse bias condition, two conduction regimes were observed. The photocurrent in low-voltage regime is limited by the transport mechanism of carriers; while in the high-voltage regime, it is limited by the density of photogenerated carriers. The Poole-Frenkel conduction mechanism was found to dominate the carrier transport in SRO under illumination. It was also demonstrated that high photosensitivity was achieved in this structure that is a potential visible optical sensor.     

Measurement method for carrier concentration in TiO2 via the Mott-Schottky approach

In direct contrast to the way in which silicon is precisely doped for integrated circuit applications in order to optimize device performance, there is little nuanced understanding of the correlation between TiO₂ doping level, charge carrier concentration, and the operation of TiO₂-based photocatalysts, dye-sensitized solar cells, and sensors. The present work outlines a rigorous methodology for the determination of free carrier concentration for doped metal oxide semiconductors such as TiO₂ that are not amenable to standard metrology methods. Undoped, Cr-, Mn-, and Nb-doped polycrystalline anatase TiO₂ are synthesized via atomic layer deposition (ALD) using Ti(OCH(CH₃)₂)₄, H₂O, Cr(C₅H₇O₂)₃, Mn(DPM)₃ (DPM = 2,2,6,6-tetramethyl-3, 5-heptanedionato), and Nb(OCH₂CH₃)₅ as the source materials for Ti, O, Cr, Mn, and Nb, respectively. Chemical composition and crystallinity are investigated and a thorough “device-like” characterization of TiO₂ Schottky diodes is carried out to justify the subsequent extraction of carrier concentration values from capacitance-voltage (C-V) measurements using the Mott-Schottky approach. The influence of factors such as substrate type, contact metal type, and surface and interface preparation are examined. Measurements of donor carrier concentration are obtained for undoped, Cr-, Mn-, and Nb-doped TiO₂ synthesized by ALD. Possible causes for the obtained carrier concentrations are discussed.     

Effect of annealing on tensile properties of electrodeposited nanocrystalline Ni with broad grain size distribution

Abstract

The microstructures and tensile properties of electrodeposited nanocrystalline Ni (nc-Ni) with a broad grain size distribution after annealing at 150, 200 and 300°C for 500 s were investigated. The as deposited broad grain size distribution nc-Ni sample exhibited a moderate strength σ_UTS of ～1107 MPa but a markedly enhanced ductility ?_TEF of ～10%, compared with electrodeposited nc-Ni with a narrow grain size distribution. Annealing below 200°C increased the strength but caused a considerably reduction in tensile elongation. This behaviour is attributed to the grain boundary relaxation and the increased order of grain boundaries after annealing, which can make the grain boundary activities, such as the grain boundary sliding and grain rotations, more difficult. Further annealing at 300°C decreased both the yield strength and tensile elongation significantly due to significant grain growth.