Huoping Xin

Hydrothermal BaTiO3 thin films on Ti-covered silicon: Characterization and growth mechanism

Polycrystalline thin films of BaTiO 3 with a resistivity of 10 3 Ω cm were fabricated on Ti-covered silicon substrates by a hydrothermal method at temperatures as low as 160°C. The films were formed by submerging the substrates in a 0.5 M Ba(OH) 3 aqueous solution sealed inside an autoclave, heating to 160°C with a saturated vapor pressure around 0.8 M Pa, and holding for various periods from 1 up to 24 h. The film thickness increased as the treatment prolonged within a certain period. The subsequent firing in air at 600°C was found to raise the resistivity substantially. The structure and properties of the films were characterized by using x-ray diffraction, scanning electron microscopy, cross-sectional transmission microscopy, Auger electron spectroscopy, Rutherford backscattering spectroscopy, and spread resistance probing. The film growth mechanism involved in hydrothermal kinetics was discussed. Three ways for hydrothermally synthesizing thick BaTiO 3 films have been recommended.

FORMATION OF COVALENT SOLID CNX COMPOUNDS BY HIGH-DOSE NITROGEN IMPLANTATION INTO CARBON THIN-FILMS

Our preliminary studies show that covalent solid CNx compounds can be synthesized by high dose nitrogen implantation into carbon thin films. 100 keV N+ ions at a dosage of 1.2×1018 cm−2 were implanted at different temperatures. The samples were evaluated by x‐ray photoelectron spectroscopy (XPS), x‐ray diffraction analysis, and Fourier transform infrared absorption spectroscopy (FTIR). N(1s) core level line XPS analyses show the existence of two different N(1s) bonding states, corresponding to the nitrogen of the C–N covalent bonding state and free state nitrogen, respectively. More importantly, it can be clearly seen that the content of C–N covalent bonding state in the samples is increased with increasing of the implanting temperature of samples. When implantation was performed at 500 °C, C(1s) XPS studies show the existence of three different C(1s) bonding states, corresponding to graphite, i‐carbon, and the carbon of C–N covalent bonding state, respectively, and FTIR analyses indicate that there is an...

Formation of BaTiO 3 and PbTiO 3 thin films under mild hydrothermal conditions

Well-crystallized polycrystalline thin films of cubic barium titanate (BaTiO 3 ) have been synthesized on Ti-covered Si substrates by exposing the substrates to a Ba(OH) 2 aqueous solution at 160 °C and a low pressure less than 1 MPa. It was presumed that the film formation of BaTiO 3 involved a dissolution-crystallization mechanism, which provides an attractive approach to produce other titanate films and powders. Also, we have used for the first time this hydrothermal technique to deposit epitaxial (001)-textured PbTiO 3 thin films on SrTiO 3 (100) substrates.

STRUCTURAL PROPERTIES OF CARBON NITRIDE FILMS PREPARED BY HIGH DOSE NITROGEN IMPLANTATION INTO CARBON THIN FILMS

Carbon nitride films were successfully prepared by ion beam synthesis method. 100 keV N+ ions at a dosage of 1.2×1018 cm−2 were implanted into carbon thin films at different temperatures. The samples were evaluated by x‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, cross‐sectional transmission electron microscopy (XTEM), Rutherford backscattering spectroscopy (RBS), x‐ray diffraction analysis (XRD), and Vickers microhardness measurement. XPS results show that most of the implanted nitrogen atoms are free state. Most of the carbon atoms have C–C bonding and a little of them form a C–N bond. It also can be clearly seen that the content of the C–N covalent bonding state in the samples is increased by raising the implanting temperature of the samples. Raman spectrum indicates that there is a Raman band near 2300 cm−1 corresponding to carbon‐nitrogen stretching. XTEM and RBS studies show that there is a buried layer of carbon nitride. XRD and TEM analyses reveal that the buried carbon nitride is pr...

FORMATION OF BURIED CARBON NITRIDE BY HIGH-DOSE NITROGEN IMPLANTATION INTO CARBON THIN-FILM

Abstract Buried carbon nitride was obtained by using 100 keV N + implantation into carbon thin film with a dose of 1.2 × 10 18 cm −2 at 500°C. N(1s) core level line X-ray photoelectron spectroscopy (XPS) analyses show the existence of two different N(1s) bonding states, corresponding to the nitrogen in a CN covalent bonding state and free state nitrogen, respectively. C(1s) XPS studies indicate the existence of three different C(1s) bonding states, corresponding to graphite, i-carbon and carbon with a CN covalent bonding state, respectively. Fourier transformation infrared absorption spectroscopy (FTIR) measurements point out that there is an absorption band near 2200 cm −1 assigned to the CN covalent bonding. Cross-sectional transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) measurements show that there is a buried carbon nitride layer. X-ray diffraction (XRD) shows the buried carbon nitride is amorphous. Vickers microhardness evaluation indicates the sample has a higher hardness than that of carbon thin film. The Implantation of Reactive Ions into Silicon (IRIS) computer program has been used to simulate the formation of the buried β-C 3 N 4 layer as N + ions are implanted into carbon. We find good agreement between experimental measurements and IRIS simulation.

Application of hydrothermal mechanism for tailor-making perovskite titanate films

In this paper, the hydrothermal preparation mechanism for BaTiO/sub 3/ films formed on Ti-covered silicon substrates was successfully applied to the preparation of other titanate films. As the result, [110]-oriented BaTiO/sub 3/ films and epitaxial PbTiO/sub 3/ films were hydrothermally grown on TiO/sub 2//Si and SrTiO/sub 3/ substrates, respectively. Finally, a method combining the hydrothermal process with sol-gel method was positively recommended and realized in the synthesis of perovskite PZT(52/48) films.

Phase evolution in boron nitride thin films prepared by a dc-gasdischarge assisted pulsed laser deposition

Boron nitride (BN) thin films were deposited on a Si (111) substrate using ArF pulsed excimer laser radiation for ablating a hexagonal BN (hBN) target and a de-gasdischarge for activating N2. The present phases in the films were determined by Fourier transformation infrared spectroscopy (FTIR). The results show that BN thin films containing largely cubic BN (cBN) phase on Si(111) substrates were successfully prepared by this de-gasdischarge assisted pulsed laser deposition (PLD). The effects of the de-gasdischarge and the chamber background gas on the formation of the cBN thin films were analyzed. The reasons for the phase evolution from hBN to cBN induced by the de-gasdischarge are discussed. The results suggested that the de-gasdischarge has two effects on the formation of cBN thin films. On one hand, it activated N2 and caused the formation of nearly stoichiometric BN films. On the other hand, it caused the activated ions to bombard the substrate and induced the formation of the cBN phase. The dual beam ion source assisted PLD method is proposed to be the most promising method in preparing cBN films.

BARUO3 THIN-FILMS PREPARED BY PULSED-LASER DEPOSITION

Abstract High electrical conductive BaRuO 3 thin films with (110) perovskite orientation have been successfully fabricated on Si(100) substrates by pulsed ArF excimer laser deposition and post-annealing. The resistivity of the films at room temperature is in the range of 10 −2 –10 −3 Ω cm. Auger electron spectroscopy (AES) measurement shows that the compositions uniformly distributed throughout the film. Rutherford backscattering spectroscopy (RBS) analysis indicates that the chemical stoichiometric ratio is well consistent with the ideal one as in BaRuO 3 .

GROWTH OF CUBIC BORON-NITRIDE THIN-FILMS BY A FIELD-IONIZATION SOURCE-ASSISTED PULSED-LASER DEPOSITION

Abstract Cubic boron nitride (cBN) thin films have been deposited on silicon (100) substrate using ArF pulsed excimer laser for ablating hexagonal boron nitride (hBN) targets and a field-ionization source for activating N 2 . The structure and composition of the films have been measured by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis and Auger electron spectroscopy (AES). The FTIR transmittance spectrum shows that there are a strong absorption peak at 1095.8 cm −1 corresponding to cBN and a very weak absorption band at 1380 cm −1 corresponding to hBN. The XRD pattern shows that there is a peak at 43.30° corresponding to the cBN (111) face. These results show that the films are mainly cBN including a small amount of hBN. AES depth-profiling experiments show that the relative atomic ratio of N to B in the films is obviously increased by using a field-ionization source of about 700 V during the deposition process.

Magnetospectroscopy of high-purity InP grown by gas source molecular beam epitaxy

Magneto-photoconductivity spectra related to the bound phonons and resonant polaron effect on Si donors in high-purity InP have been investigated. Not only the transition from the 1s ground state to bound phonon state (1s+LO) of Si donors, but also the antilevel crossings of the (3, 1, 0) metastable state with the bound phonon states (1s+LO) and (2p−1+LO) are clearly observed in high magnetic fields. The results demonstrate the bound phonon in Si-doped InP consists of both electron and phonon via multiphonon processes and there is a resonant interaction between LO phonons and impurity-bound electrons in InP.