Guosheng Shao - Academia.edu (original) (raw)
Papers by Guosheng Shao
Nature, 2001
... Letters to Nature. Nature 414, 470 (22 November 2001) | doi :10.1038/35106615. addendum: An e... more ... Letters to Nature. Nature 414, 470 (22 November 2001) | doi :10.1038/35106615. addendum: An efficient room-temperature silicon-based light-emitting diode. Wai Lek Ng, MA Lourenço, RM Gwilliam, S. Ledain, G. Shao & KP Homewood. Nature 410,192–194 (2001). ...
CuO thin films with different levels of compositional deviation from 50:50 stoichiometry have bee... more CuO thin films with different levels of compositional deviation from 50:50 stoichiometry have been fabricated using radiofrequency sputtering deposition wherein the sputtering gases consisted of oxygen and argon in various proportions. The microstructures of the thin films were characterized by combining a series of advanced methods including X-ray diffraction, energy dispersive X-ray analysis, scanning and high-resolution transmission electron microscopy, electron energy loss spectroscopy, and high-resolution X-ray photoelectron spectroscopy. The results showed that the chemical states of Cu and O in the thin films depended upon CuO composition and sputtering conditions, so that different levels of Cu vacancies dictated the electrical/electronic properties of the thin films. The ability to control the compound composition and associated alloying chemistry enables tuning of the concentration and mobility of holes in CuO, hence creating alow-cost and environmentally friendly semiconductor from abundant materials. This offers an essential technical basis in engineering photonic devices such as pn or Schottky diodes, thus opening new avenues for economic harvest of solar energy using diodes solely based on sustainable oxides.
Superlattices and Microstructures, 2015
AgBr/AgCl-Ag nanocrystals with various molar Br-to-Ag ratios (R Br/Ag = 0, 1/3, 1/2, 2/3, 1) and ... more AgBr/AgCl-Ag nanocrystals with various molar Br-to-Ag ratios (R Br/Ag = 0, 1/3, 1/2, 2/3, 1) and different photoreduction times (0-20 min) were synthesized via stepwise liquid-solid reactions using the freeze-dried PVP-Ag + hybrid as the Ag source, followed by a photoreduction reaction. The AgBr/AgCl-Ag 7.5 (1:2) nanocrystals obtained take on a spherical morphology with a particle-size range of 58 ± 15 nm. The photocatalytic performance of AgBr/AgCl-Ag nanocrystals was evaluated by photodegrading organic dyes, 4-chlorophenol and isopropanol under artificial visible light (k P 420 nm, 100 mW cm À2 ). For the decomposition of rhodamine B, the AgBr/AgCl-Ag 7.5 (1:2) nanocrystals has a photodegradation rate of 0.87minAˋ1,0.87 min À1 , 0.87minAˋ1,159 times higher than that ($0.0054 min À1 ) of TiO 2 (P25), whereas the AgCl-Ag and AgBr-Ag nanocrystals have photodegradation rates of 0.35 min À1 and 0.45 min À1 , respectively. The efficient separation of photogenerated electron-hole pairs in the ternary system consisting of AgBr, http://dx.
RSC Adv., 2015
Hierarchical Fe 2 O 3 @WO 3 nanocomposites with ultrahigh specific areas, consisting of Fe 2 O 3 ... more Hierarchical Fe 2 O 3 @WO 3 nanocomposites with ultrahigh specific areas, consisting of Fe 2 O 3 nanoparticles (NPs) and single-crystal WO 3 nanoplates, were synthesized via a microwave-heating (MH) in situ growth process. WO 3 nanoplates were derived by an intercalation and topochemical-conversion route, and the Fe 2 O 3 NPs were in situ grown on the WO 3 surfaces via a heterogamous nucleation. The water-bathheating (WH) process was also developed to synthesize a Fe 2 O 3 @WO 3 nanocomposite for comparison purposes. The techniques of X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the samples obtained. The results show that a-Fe 2 O 3 NPs with a size range of 5-10 nm are uniformly, tightly anchored on the surfaces of WO 3 nanoplates in the Fe 2 O 3 @WO 3 samples obtained via the MH process, whereas the a-Fe 2 O 3 NPs are not uniform in particle-sizes and spatial distribution in the Fe 2 O 3 @WO 3 samples obtained via the WH process. The BET surface area of the 5wt%Fe 2 O 3 @WO 3 sample derived by the MH process is as high as 1207 m 2 g À1 , 5.9 times higher than that (203 m 2 g À1 ) of the corresponding WO 3 nanoplates. The dramatic enhancement in the specific surface area of the Fe 2 O 3 @WO 3 samples should be attributed to the hierarchical microstructure, which makes the internal surfaces or interfaces in aggregated polycrystals be fully outside surfaces via a house-of-cards configuration, where the singlelayered and disconnected Fe 2 O 3 NPs are tightly anchored on the surfaces of the WO 3 nanoplates. The gas-sensing properties of the Fe 2 O 3 @WO 3 sensors were investigated. The gas-sensors based on the Fe 2 O 3 @WO 3 obtained via the MH process show a high response and selectivity to H 2 S at low operating temperatures. The 5%Fe 2 O 3 @WO 3 sample shows the highest H 2 S-sensing response at 150 C. Its response to 10 ppm H 2 S is as high as 192, 4 times higher than that of the WO 3 -nanoplate sensor. The improvement in the gas-sensing performance of the Fe 2 O 3 @WO 3 nanocomposites can be attributed to the synergistic effect in compositions and the hierarchical microstructures with ultrahigh specific surface areas.
Either rutile or anatase vertical orientated TiO2 array films were synthesized successfully on FT... more Either rutile or anatase vertical orientated TiO2 array films were synthesized successfully on FTO (F: SnO2) substrate via hydrothermal method through controlling the concentration of Cl^- and SO4^2-. The density of nanorods can be adjusted by varying the volume ratio of ethanol/water, and the degree of orientation and crystallinity of TiO2 nanofilms were enhanced with increasing dosage of ethanol. Meanwhile, completely dense anatase films with [004] oriented growth appear within a very narrow concentration window when adding sulfuric acid into precursor. Besides, other alcohols such as methanol, n-propanol and n-butyl were also used as solvent to examine the role of alcohol type during hydrothermal process for both two phase films. The growth rate and degree of perpendicular orientation declined as the alkyl length of solvents increases. Hydrogen sensing characteristics of dense films of both rutile and anatase phases showed that there was a remarkable improvement of sensitivity re...
Physics, Chemistry and Application of Nanostructures - Reviews And Short Notes To Nanomeeting-2001, 2001
ABSTRACT
SCS 2003 International Symposium on Signals Circuits and Systems Proceedings (Cat No 03EX720) IIT-02, 2002
Semiconducting precipitates of β β β βFeSi 2 have been successfully fabricated in silicon by high... more Semiconducting precipitates of β β β βFeSi 2 have been successfully fabricated in silicon by high dose Fe + implantation (typically 1.5 x 10 16 Fe cm -2 at 200keV). Room temperature electro luminescence (EL) at 1.5µ µ µ µm has been observed from light emitting diodes (LED's) incorporating this type of structure. This study is to evaluate how the microstructure and optical properties are affected by the implantation parameters, in particular the role of implantation temperature, when high beam current densities are being used. This was done in order to evaluate whether the implant period could be reduced to a commercially realistic time without adversely affecting the optical properties. In this study the implantation temperature was varied and the resulting structures investigated (before and after annealing) using optical absorption, Fourier Transform Infrared Spectroscopy (FTIR), Rutherford backscattering spectroscopy (RBS) and cross sectional transmission electron microscopy (XTEM). A 70 meV decrease in the optical band gap was observed between a sample implanted at 250°°°°C and one implanted at 550°°°°C, a shift in the FTIR spectrum was also observed. RBS and XTEM measurements showed that this change was associated with a change from a surface to a buried silicide "layer", with the latter also exhibiting room temperature EL.
Nanoscale, Jan 21, 2014
Hierarchical SnO2@rGO nanostructures with superhigh surface areas are synthesized via a simple re... more Hierarchical SnO2@rGO nanostructures with superhigh surface areas are synthesized via a simple redox reaction between Sn(2+) ions and graphene oxide (GO) nanosheets under microwave irradiation. XRD, SEM, TEM, XPS, TG-DTA and N2 adsorption-desorption are used to characterize the compositions and microstructures of the SnO2@rGO samples obtained. The SnO2@rGO nanostructures are used as gas-sensing and electroactive materials to evaluate their property-microstructure relationship. The results show that SnO2 nanoparticles (NPs) with particle sizes of 3-5 nm are uniformly anchored on the surfaces of reduced graphene oxide (rGO) nanosheets through a heteronucleation and growth process. The as-obtained SnO2@rGO sample with a hierarchically sesame cake-like microstructure and a superhigh specific surface area of 2110.9 m(2) g(-1) consists of 92 mass% SnO2 NPs and ∼8 mass% rGO nanosheets. The sensitivity of the SnO2@rGO sensor upon exposure to 10 ppm H2S is up to 78 at the optimal operating t...
This paper presents a study of the synthesis of beta-FeSi2 layers by irradiation of Fe/Si bilayer... more This paper presents a study of the synthesis of beta-FeSi2 layers by irradiation of Fe/Si bilayers with Fe+ ions and a consequent thermal processing, and the analysis of their properties. Characterization of samples included RBS, XRD, cross-section HRTEM, and photo-absorption measurements. It was found that homogenous, highly ordered 275 nm beta-FeSi2 layers can be grown by implantation of 90 nm
A p-type device grade silicon wafer was implanted by 1 MeV Ru+ ions to a dose of 5.67 × 1016 cm-2... more A p-type device grade silicon wafer was implanted by 1 MeV Ru+ ions to a dose of 5.67 × 1016 cm-2. The microstructures of the as-implanted and annealed samples were studied mainly by analytical transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the implantation resulted in a well-defined surface layer of about 910 nm in thickness.
ABSTRACT In this paper we describe a new approach to the manufacture of Si based optical emitters... more ABSTRACT In this paper we describe a new approach to the manufacture of Si based optical emitters. Dislocation engineering, using entirely ULSI compatible technology has been shown to be a viable route to the production of efficient LED's operating at room temperature. External quantum efficiencies of ~ 10-4 have been realised for un-packaged devices operating at room temperature. This approach has also been shown to yield great benefits in the control of thermal quenching for other material systems, such as the FeSi2, where room temperature operational devices based at 1.5um have been demonstrated
Room temperature b-FeSi 2 light emitting diodes have been fabricated by conventional ULSI process... more Room temperature b-FeSi 2 light emitting diodes have been fabricated by conventional ULSI processes using a recently developed dislocation engineering approach. The devices were fabricated by iron implantation into pre-grown abrupt silicon p-n junctions followed by low energy boron implantation to form the dislocation loops. Room temperature emission at $1.6 lm was obtained from most of the dislocation engineered devices, in contrast to standard ion beam synthesised b-FeSi 2 diodes, where no electroluminescence was observed.
ABSTRACT In this work, TiO2 thin films were prepared by RF sputtering onto thermally grown oxide ... more ABSTRACT In this work, TiO2 thin films were prepared by RF sputtering onto thermally grown oxide layers on Si substrates. Cobalt and iron implantation into the TiO2 films was performed using a metal vapor vacuum arc ion source. The as-implanted and annealed films were characterized using Rutherford backscattering spectrometry, transmission electron microscopy, x-ray diffractometry, x-ray photoelectron spectroscopy, spectroscopic ellipsometry, and vibrating sample magnetometry. The dependence of the magnetic properties on the implantation and annealing conditions were studied in detail. Clear room temperature ferromagnetic properties (RT FM) were observed. The saturation magnetization (Ms) values per implanted Co or Fe atom exhibit an oscillatory dependence on the implantation dose. The maximum Ms in one Co implanted samples was determined to be 2.3 μB/Co, exceeding the bulk Co value. The possible origins of the RT FM properties are discussed.
Although silicon is the preferred material for mainstream microelectronic applications, light emi... more Although silicon is the preferred material for mainstream microelectronic applications, light emission from silicon is inefficient due to its indirect band gap. Despite this intrinsic problem, many approaches have been tried to obtain light emission in silicon-based devices. Porous silicon [1], silicon/silicon dioxide superlattices [2], silicon nanoprecipitates in silicon dioxide , erbium in silicon [4], silicon/germanium , and iron disilicide [6] are potential routes. However, a common problem found in these devices is the strong thermal quenching of the luminescence leading to very poor performance at room temperature.
Ternary Fe(Os)Si 2 alloys, a novel semiconducting opto-electronic material with a tuneable direct... more Ternary Fe(Os)Si 2 alloys, a novel semiconducting opto-electronic material with a tuneable direct band gap property, was designed by energy-band engineering. The electronic structures of FeSi 2 , OsSi 2 and (FeOs)Si 2 were theoretically calculated using the density functional theory (DFT) method. The thin films were fabricated by magnetic co-sputtering deposition, so as to substitute the Fe sublattice sites by Os. X-ray diffraction, energy dispersion X-ray spectrometry and optical absorption spectroscopy were used to characterize the structural properties of the thin films. Experimental results showed that all the Fe 1-
Silicide-based photonic materials have attracted a great deal of research interest due to their c... more Silicide-based photonic materials have attracted a great deal of research interest due to their compatibility with the well-developed silicon technology. Extensive efforts have been made for the synthesis and characterisation of these materials. This paper covers some aspects of the microstructural and crystallographic characteristics of ion beam synthesised silicides such as the semiconducting iron and ruthenium silicides, using transmission electron microscopy. A previously predicted new orientation relationship has been found to exist between the Si substrate and ion beam synthesised βFeSi 2 nanocrystals, which are free of 90°r otational order domain boundaries.
Nature, 2001
... Letters to Nature. Nature 414, 470 (22 November 2001) | doi :10.1038/35106615. addendum: An e... more ... Letters to Nature. Nature 414, 470 (22 November 2001) | doi :10.1038/35106615. addendum: An efficient room-temperature silicon-based light-emitting diode. Wai Lek Ng, MA Lourenço, RM Gwilliam, S. Ledain, G. Shao & KP Homewood. Nature 410,192–194 (2001). ...
CuO thin films with different levels of compositional deviation from 50:50 stoichiometry have bee... more CuO thin films with different levels of compositional deviation from 50:50 stoichiometry have been fabricated using radiofrequency sputtering deposition wherein the sputtering gases consisted of oxygen and argon in various proportions. The microstructures of the thin films were characterized by combining a series of advanced methods including X-ray diffraction, energy dispersive X-ray analysis, scanning and high-resolution transmission electron microscopy, electron energy loss spectroscopy, and high-resolution X-ray photoelectron spectroscopy. The results showed that the chemical states of Cu and O in the thin films depended upon CuO composition and sputtering conditions, so that different levels of Cu vacancies dictated the electrical/electronic properties of the thin films. The ability to control the compound composition and associated alloying chemistry enables tuning of the concentration and mobility of holes in CuO, hence creating alow-cost and environmentally friendly semiconductor from abundant materials. This offers an essential technical basis in engineering photonic devices such as pn or Schottky diodes, thus opening new avenues for economic harvest of solar energy using diodes solely based on sustainable oxides.
Superlattices and Microstructures, 2015
AgBr/AgCl-Ag nanocrystals with various molar Br-to-Ag ratios (R Br/Ag = 0, 1/3, 1/2, 2/3, 1) and ... more AgBr/AgCl-Ag nanocrystals with various molar Br-to-Ag ratios (R Br/Ag = 0, 1/3, 1/2, 2/3, 1) and different photoreduction times (0-20 min) were synthesized via stepwise liquid-solid reactions using the freeze-dried PVP-Ag + hybrid as the Ag source, followed by a photoreduction reaction. The AgBr/AgCl-Ag 7.5 (1:2) nanocrystals obtained take on a spherical morphology with a particle-size range of 58 ± 15 nm. The photocatalytic performance of AgBr/AgCl-Ag nanocrystals was evaluated by photodegrading organic dyes, 4-chlorophenol and isopropanol under artificial visible light (k P 420 nm, 100 mW cm À2 ). For the decomposition of rhodamine B, the AgBr/AgCl-Ag 7.5 (1:2) nanocrystals has a photodegradation rate of 0.87minAˋ1,0.87 min À1 , 0.87minAˋ1,159 times higher than that ($0.0054 min À1 ) of TiO 2 (P25), whereas the AgCl-Ag and AgBr-Ag nanocrystals have photodegradation rates of 0.35 min À1 and 0.45 min À1 , respectively. The efficient separation of photogenerated electron-hole pairs in the ternary system consisting of AgBr, http://dx.
RSC Adv., 2015
Hierarchical Fe 2 O 3 @WO 3 nanocomposites with ultrahigh specific areas, consisting of Fe 2 O 3 ... more Hierarchical Fe 2 O 3 @WO 3 nanocomposites with ultrahigh specific areas, consisting of Fe 2 O 3 nanoparticles (NPs) and single-crystal WO 3 nanoplates, were synthesized via a microwave-heating (MH) in situ growth process. WO 3 nanoplates were derived by an intercalation and topochemical-conversion route, and the Fe 2 O 3 NPs were in situ grown on the WO 3 surfaces via a heterogamous nucleation. The water-bathheating (WH) process was also developed to synthesize a Fe 2 O 3 @WO 3 nanocomposite for comparison purposes. The techniques of X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the samples obtained. The results show that a-Fe 2 O 3 NPs with a size range of 5-10 nm are uniformly, tightly anchored on the surfaces of WO 3 nanoplates in the Fe 2 O 3 @WO 3 samples obtained via the MH process, whereas the a-Fe 2 O 3 NPs are not uniform in particle-sizes and spatial distribution in the Fe 2 O 3 @WO 3 samples obtained via the WH process. The BET surface area of the 5wt%Fe 2 O 3 @WO 3 sample derived by the MH process is as high as 1207 m 2 g À1 , 5.9 times higher than that (203 m 2 g À1 ) of the corresponding WO 3 nanoplates. The dramatic enhancement in the specific surface area of the Fe 2 O 3 @WO 3 samples should be attributed to the hierarchical microstructure, which makes the internal surfaces or interfaces in aggregated polycrystals be fully outside surfaces via a house-of-cards configuration, where the singlelayered and disconnected Fe 2 O 3 NPs are tightly anchored on the surfaces of the WO 3 nanoplates. The gas-sensing properties of the Fe 2 O 3 @WO 3 sensors were investigated. The gas-sensors based on the Fe 2 O 3 @WO 3 obtained via the MH process show a high response and selectivity to H 2 S at low operating temperatures. The 5%Fe 2 O 3 @WO 3 sample shows the highest H 2 S-sensing response at 150 C. Its response to 10 ppm H 2 S is as high as 192, 4 times higher than that of the WO 3 -nanoplate sensor. The improvement in the gas-sensing performance of the Fe 2 O 3 @WO 3 nanocomposites can be attributed to the synergistic effect in compositions and the hierarchical microstructures with ultrahigh specific surface areas.
Either rutile or anatase vertical orientated TiO2 array films were synthesized successfully on FT... more Either rutile or anatase vertical orientated TiO2 array films were synthesized successfully on FTO (F: SnO2) substrate via hydrothermal method through controlling the concentration of Cl^- and SO4^2-. The density of nanorods can be adjusted by varying the volume ratio of ethanol/water, and the degree of orientation and crystallinity of TiO2 nanofilms were enhanced with increasing dosage of ethanol. Meanwhile, completely dense anatase films with [004] oriented growth appear within a very narrow concentration window when adding sulfuric acid into precursor. Besides, other alcohols such as methanol, n-propanol and n-butyl were also used as solvent to examine the role of alcohol type during hydrothermal process for both two phase films. The growth rate and degree of perpendicular orientation declined as the alkyl length of solvents increases. Hydrogen sensing characteristics of dense films of both rutile and anatase phases showed that there was a remarkable improvement of sensitivity re...
Physics, Chemistry and Application of Nanostructures - Reviews And Short Notes To Nanomeeting-2001, 2001
ABSTRACT
SCS 2003 International Symposium on Signals Circuits and Systems Proceedings (Cat No 03EX720) IIT-02, 2002
Semiconducting precipitates of β β β βFeSi 2 have been successfully fabricated in silicon by high... more Semiconducting precipitates of β β β βFeSi 2 have been successfully fabricated in silicon by high dose Fe + implantation (typically 1.5 x 10 16 Fe cm -2 at 200keV). Room temperature electro luminescence (EL) at 1.5µ µ µ µm has been observed from light emitting diodes (LED's) incorporating this type of structure. This study is to evaluate how the microstructure and optical properties are affected by the implantation parameters, in particular the role of implantation temperature, when high beam current densities are being used. This was done in order to evaluate whether the implant period could be reduced to a commercially realistic time without adversely affecting the optical properties. In this study the implantation temperature was varied and the resulting structures investigated (before and after annealing) using optical absorption, Fourier Transform Infrared Spectroscopy (FTIR), Rutherford backscattering spectroscopy (RBS) and cross sectional transmission electron microscopy (XTEM). A 70 meV decrease in the optical band gap was observed between a sample implanted at 250°°°°C and one implanted at 550°°°°C, a shift in the FTIR spectrum was also observed. RBS and XTEM measurements showed that this change was associated with a change from a surface to a buried silicide "layer", with the latter also exhibiting room temperature EL.
Nanoscale, Jan 21, 2014
Hierarchical SnO2@rGO nanostructures with superhigh surface areas are synthesized via a simple re... more Hierarchical SnO2@rGO nanostructures with superhigh surface areas are synthesized via a simple redox reaction between Sn(2+) ions and graphene oxide (GO) nanosheets under microwave irradiation. XRD, SEM, TEM, XPS, TG-DTA and N2 adsorption-desorption are used to characterize the compositions and microstructures of the SnO2@rGO samples obtained. The SnO2@rGO nanostructures are used as gas-sensing and electroactive materials to evaluate their property-microstructure relationship. The results show that SnO2 nanoparticles (NPs) with particle sizes of 3-5 nm are uniformly anchored on the surfaces of reduced graphene oxide (rGO) nanosheets through a heteronucleation and growth process. The as-obtained SnO2@rGO sample with a hierarchically sesame cake-like microstructure and a superhigh specific surface area of 2110.9 m(2) g(-1) consists of 92 mass% SnO2 NPs and ∼8 mass% rGO nanosheets. The sensitivity of the SnO2@rGO sensor upon exposure to 10 ppm H2S is up to 78 at the optimal operating t...
This paper presents a study of the synthesis of beta-FeSi2 layers by irradiation of Fe/Si bilayer... more This paper presents a study of the synthesis of beta-FeSi2 layers by irradiation of Fe/Si bilayers with Fe+ ions and a consequent thermal processing, and the analysis of their properties. Characterization of samples included RBS, XRD, cross-section HRTEM, and photo-absorption measurements. It was found that homogenous, highly ordered 275 nm beta-FeSi2 layers can be grown by implantation of 90 nm
A p-type device grade silicon wafer was implanted by 1 MeV Ru+ ions to a dose of 5.67 × 1016 cm-2... more A p-type device grade silicon wafer was implanted by 1 MeV Ru+ ions to a dose of 5.67 × 1016 cm-2. The microstructures of the as-implanted and annealed samples were studied mainly by analytical transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the implantation resulted in a well-defined surface layer of about 910 nm in thickness.
ABSTRACT In this paper we describe a new approach to the manufacture of Si based optical emitters... more ABSTRACT In this paper we describe a new approach to the manufacture of Si based optical emitters. Dislocation engineering, using entirely ULSI compatible technology has been shown to be a viable route to the production of efficient LED's operating at room temperature. External quantum efficiencies of ~ 10-4 have been realised for un-packaged devices operating at room temperature. This approach has also been shown to yield great benefits in the control of thermal quenching for other material systems, such as the FeSi2, where room temperature operational devices based at 1.5um have been demonstrated
Room temperature b-FeSi 2 light emitting diodes have been fabricated by conventional ULSI process... more Room temperature b-FeSi 2 light emitting diodes have been fabricated by conventional ULSI processes using a recently developed dislocation engineering approach. The devices were fabricated by iron implantation into pre-grown abrupt silicon p-n junctions followed by low energy boron implantation to form the dislocation loops. Room temperature emission at $1.6 lm was obtained from most of the dislocation engineered devices, in contrast to standard ion beam synthesised b-FeSi 2 diodes, where no electroluminescence was observed.
ABSTRACT In this work, TiO2 thin films were prepared by RF sputtering onto thermally grown oxide ... more ABSTRACT In this work, TiO2 thin films were prepared by RF sputtering onto thermally grown oxide layers on Si substrates. Cobalt and iron implantation into the TiO2 films was performed using a metal vapor vacuum arc ion source. The as-implanted and annealed films were characterized using Rutherford backscattering spectrometry, transmission electron microscopy, x-ray diffractometry, x-ray photoelectron spectroscopy, spectroscopic ellipsometry, and vibrating sample magnetometry. The dependence of the magnetic properties on the implantation and annealing conditions were studied in detail. Clear room temperature ferromagnetic properties (RT FM) were observed. The saturation magnetization (Ms) values per implanted Co or Fe atom exhibit an oscillatory dependence on the implantation dose. The maximum Ms in one Co implanted samples was determined to be 2.3 μB/Co, exceeding the bulk Co value. The possible origins of the RT FM properties are discussed.
Although silicon is the preferred material for mainstream microelectronic applications, light emi... more Although silicon is the preferred material for mainstream microelectronic applications, light emission from silicon is inefficient due to its indirect band gap. Despite this intrinsic problem, many approaches have been tried to obtain light emission in silicon-based devices. Porous silicon [1], silicon/silicon dioxide superlattices [2], silicon nanoprecipitates in silicon dioxide , erbium in silicon [4], silicon/germanium , and iron disilicide [6] are potential routes. However, a common problem found in these devices is the strong thermal quenching of the luminescence leading to very poor performance at room temperature.
Ternary Fe(Os)Si 2 alloys, a novel semiconducting opto-electronic material with a tuneable direct... more Ternary Fe(Os)Si 2 alloys, a novel semiconducting opto-electronic material with a tuneable direct band gap property, was designed by energy-band engineering. The electronic structures of FeSi 2 , OsSi 2 and (FeOs)Si 2 were theoretically calculated using the density functional theory (DFT) method. The thin films were fabricated by magnetic co-sputtering deposition, so as to substitute the Fe sublattice sites by Os. X-ray diffraction, energy dispersion X-ray spectrometry and optical absorption spectroscopy were used to characterize the structural properties of the thin films. Experimental results showed that all the Fe 1-
Silicide-based photonic materials have attracted a great deal of research interest due to their c... more Silicide-based photonic materials have attracted a great deal of research interest due to their compatibility with the well-developed silicon technology. Extensive efforts have been made for the synthesis and characterisation of these materials. This paper covers some aspects of the microstructural and crystallographic characteristics of ion beam synthesised silicides such as the semiconducting iron and ruthenium silicides, using transmission electron microscopy. A previously predicted new orientation relationship has been found to exist between the Si substrate and ion beam synthesised βFeSi 2 nanocrystals, which are free of 90°r otational order domain boundaries.