Given the global water challenges, solar-driven steam generation has become a renewed topic recently as an energy-efficient way for clean water production. Here, a hybrid plasmonic structure consisting of a top layer of TiN nanoparticles (NPs) and a bottom layer of mesoporous anodized alumina membrane (AAM) was rationally designed and fabricated. The top TiN NPs with broadband light absorption acted as a plasmonic heating layer, which converted the absorbed light to heat efficiently for interfacial water heating. The AAM acted as the mechanical support layer, guaranteeing the heat isolation and continuous water replenishment. With optimized thickness of the TiN top layer, a solar steam generation efficiency of 87.7% was achieved in this study. This efficiency is comparable or even higher than prior studies. The current work proves the capability of the TiN NPs as an alternative photothermal material.

In this study, the authors have comparatively studied the influence of H2 addition on the structures and properties of ZnO films grown by metal organic (MO) chemical vapor deposition with dimethyl zinc and diethyl zinc as zinc precursors and N2O and O2 as oxygen sources, respectively. Various characterization methods, like x-ray diffraction, Raman scattering, Hall effect, photoluminescence, and atomic force microscopy, have been utilized, showing that H2 has different effects on different MO precursors and oxidants. The H2 addition has significantly improved the crystal structural quality of ZnO thin films for the case of dimethyl zinc source, but an opposite effect has been found for the case of diethyl zinc. Moreover, the H2 addition can significantly improve the optical properties of the ZnO films, regardless of the zinc MO sources used, with the surface morphology improved too. The suppression of carbon-related contaminations depends on the use of different precursors and whether H2 is added. By analyzing the experimental results, we have given the effects of H2 on the decomposition of the discussed MO precursors and oxidants, the proposed mechanism could be used in understanding the experimental data.

Transmission electron microscopy (TEM), x-ray diffraction (XRD), photoluminescence (PL) and Raman scattering measurements were applied to study the correlation between the microstructure and physical properties of the GaN films grown by light radiation heating metalorganic chemical vapor deposition (LRH-MOCVD), using GaN buffer layer on sapphire substrates. When the density of the threading dislocation (TD) increases about one order of magnitude, the yellow luminescence (YL) intensity is strengthened from negligible to two orders of magnitude higher than the band edge emission intensity. The full width of half maximum (FWHM) of the GaN (0002) peak of the XRD rocking curve was widened from 11 min to 15 min, and in Raman spectra, the width of E2 mode is broadened from 5 cm−1 to 7 cm−1. A “zippers” structure at the interface of GaN/sapphire was observed by high-resolution electron microscope (HREM). Furthermore the origins of TD and relationship between physical properties and microstructures combining the growth conditions are discussed.

Transmission electron microscopy (TEM), x-ray diffraction (XRD), photoluminescence (PL) and Raman scattering measurements were applied to study the correlation between the microstructure and physical properties of the GaN films grown by light radiation heating metalorganic chemical vapor deposition (LRH-MOCVD), using GaN buffer layer on sapphire substrates. When the density of the threading dislocation (TD) increases about one order of magnitude, the yellow luminescence (YL) intensity is strengthened from negligible to two orders of magnitude higher than the band edge emission intensity. The full width of half maximum (FWHM) of the GaN (0002) peak of the XRD rocking curve was widened from 11 min to 15 min, and in Raman spectra, the width of E2 mode is broadened from 5 cm-1 to 7 cm-1. A “zippers” structure at the interface of GaN/sapphire was observed by high-resolution electron microscope (HREM). Furthermore the origins of TD and relationship between physical properties and microstructures combining the growth conditions are discussed.

In this paper, we report on the experiment results of wet oxidation of Si1-xGex on SiO2. AES and XPS measurements were performed to study the effect of the oxidation on the Si1-xGex layer. A possible mechanism was proposed.

Modulation Extrinsic photoconductivity spectra between 1.44eV and 1.75eV of unintentionally n-doped high resistance GaN film grown by MOCVD are measured at room temperature by using wavelength adjustable Ti:Sapphire laser. We find that there are two major deep levels in the GaN material in the used photon energy range. The relaxation time of excess carriers controlled by those levels are in the order of 10−4sec. The concentration of localized states are determined as 1.8×108cm−3 and 2.5×109cm−3, respectively. A physical model is developed to explain the results and process the data. Using a new method we have determined the optical absorption cross section of deep levels are 1.5×10−17cm2 and 2.7×10−18cm2, respectively.

In this paper, we reported experimental results about optical and structural properties of amorphous silicon carbide (α-Si1-xCx). The films of a-Si1-xCx) were grown by CVD on substrate of quartz glass. Optical constants (n-refractive index, a-absorption coefficient, Eg-optical energy band gap) of these films were determined by transmission spectra. The radial distribution functions (RDFs) of α- Sil−xCx) films were drawn out from the data of x-ray diffraction spectra. According to the RDFs, we imagined the statistic scene from which we could obtain the information of atomic radial distribution. The bond lengths and bond numbers of Si-Si, Si-C, and C-C could be also determined by RDFs. From the analysis of Raman spectra, we obtained the information of their vibration state density, and discerned the peaks of bond vibration, which agreed well with the results of α-Si1-xCx) RDF.

In this paper we employed the TSC method to investigate the traps in GaN. The measured sample was a M-S-M UV-detector of high-resistance GaN on sapphire grown by LP-MOCVD. The relation of dark conductance to temperature clearly showed three major donor levels at 0.019, 0.13 and 0.74eV respectively. TSC measurements from 60 to 380K indicated that there were at least 11 traps in the GaN material. The active energy of those traps were 0.15, 0.19, 0.25, 0.28, 0.33, 0.39, 0.47, 0.55, 0.60, 0.63 and 0.67eV. The range of trap density is from 6 × l014cm-3 to 2 × l018cm-3. By comparing TSC spectrum to dark current, we consider there are at least 4 hole traps in the measured range with energy of 0.25, 0.28, 0.33 and 0.39eV. The illumination time effect was studied and discussed.

We have observed a negative differential resistivity (NDR) in metal-semiconductor-metal (M-S-M) photoconductor made from unintentionally doped GaN grown by metalorganic chemical vapor deposition. The threshold field for the onset of NDR was found to be independent of the spacing of M-S-M fingers, and was measured to be 1.91×105 V/cm for GaN with an n-type carrier concentration of 1014 cm−3. We believe that the observed NDR is due to transferred electron effect in GaN. The threshold field value is very close to the value obtained from the theoretical simulation. This observation, to the best of our knowledge, is the first experimental evidence of transferred-electron effects in GaN, which is important in understanding GaN energy band structure and in the application of Gunn-effect devices using GaN materials.

The transition energy, the binding energy, the intensity, the broadening and the lifetime of the free-exciton transitions in GaAs epitaxial layer have well been investigated using photoconductivity measurement which is analyzed in term of an improved fitting model. We have found that as the thickness is increased, the bind energy increases, but both the intensity of the high excitonic level and the lifetime of the excitons decrease. These effects are attributed mainly to imperfections located near the surface of the epitaxial layer.

Using lithography, and selective etching the Si1-xGex/Si multiple quantum well wires are fabricated. The characteristics of the selective chemical etching of Si1-xGex and Si are investigated, and high-performance etchants are developed. The etchant composed of HF:NH4F:H202:NH4OH is used for the etching of the epitaxial Si1-xGex films, the selectivity is better than 250 for Si0.76Ge0.24, and increases with the increase of the mole fraction x of Ge. Another etchant composed of NH4NO3:NH4OH is used for the etching of Si, the selectivity is higher than 1000 ( x ≥ 0.1 ). A preliminary photoluminescence (PL) result obtained from the Si0.76Ge0.24 multiple quantum well wires is presented. As the linewidth of the wires is reduced down to 50 nm, an intense complicated PL spectrum in the wavelength range of 500∼800 nm is observed at liquid nitrogen temperature. The origin of such spectrum is unclear.

In this paper, we calculated theoretically the strain distribution and the critical thickness of the SiGe epilayers on Si(100) mesa structural substrates by considering the effect of the compliance of substrates, along with the effect of the limited area, and found that the compliance of substrates was relevant not only to its thickness, but also to their lateral size. The introduction of substrate compliance significantly reduced the total strain energy in the epilayers, and increased the critical thickness. That approach was realized by growth on the mesa substrates. The TEM observations confirmed the results of calculations.

In this paper we report the influence of H2 on Ge surface segregation in Si/SiGe heterostructures. The sample were grown on Si(001) substrate tinder different gas flow of H2 by RTP/VLP-CVD. Auger electron energy spectroscopy(AES) has been used to determine the Ge distribution in Si/SiGe heterostructures. The results indicate that H2 can strongly alter the mechanism of Ge surface segregation and change the distribution of Ge atoms.

SiH4 and GeH4 Deposition and In-Situ Doping of SiGe/Si Strained Heterostructures by Rapid Thermal Process Very Low Pressure Chemical Vapor Deposition method have been studied in this paper. Ge incorporation rate increases to a maximum value and then decreases as temperature increases, the growth rate of SiGe alloy reaches its maximum value and then decreases as Ge composition increases. Ge incorporation also enhances Si deposition rate in SiGe alloy. The Boron and Phosphorus doping would change thegrowth rate of SiGe layers and the sharp doping interfaces in SiGe/Si heterostructures have been obtained.

In this paper, we will report fabrication and structure study of single crystal β-SiC film on Si substrate by hot-filament chemical vapor deposition (HFC VD). The reaction sources are hydrogen-diluted methane(CH4) and Silane(SiH4). The wafer surface temperature is about 650°C. The typical growth rate is 200nm/h. Raman scattering spectrum shows a peak centering at 960cm-1 with a full width at half magnitude (FWHM) of 75cm-1. At room temperature, the photoluminescence spectrum gives a wide band at 580nm (2.2eV) with a FWHM of 55nm. Fourier transmission infrared (FT-IR) spectrum exhibits an absorption peak at 12.6 μm XRD and XPS analysis indicate that the epilayer is a stoichiometrical single crystal cubic silicon carbide film.

In this paper we report for the first time theoretical and experimental study on smallpulse DLTS measurements of deep levels in semiconductor heterostructures. A theoretical model has been developed on the basis of the Schodinger and Poisson's electrostatic equation. Distribution of charge density in the superlattice has been considered, especially transferred charges in the “narrow gap” sublayers. The calculated results indicate that tinder the 1017/cm3 doping condition, a 30mV small pulse corresponds to a 2nm “sampling space window”, it is enough to detect special signal of deep levels in each sublayer in the semiconductor heterostructures. A SiGe/Si sample has been measured by the small-pulse DLTS. The experimental results agree well with the theoretical prediction and show that the small-pulse DLTS is a good method to study deep levels in the semiconductor heterostructures.

A single crystal GaAs/Si heterostructure has been fabricated using the “two step” version of the traditional halogenide VPE technique. The X-ray diffraction spectroscopy, the high resolution electron microscopy observation and the Raman scattering spectroscopy have been used to analyze the structure of the GaAs epitaxial film on Si, while the X-ray photoelectron energy spectroscopy has been used to determine the chemical structure of the GaAs epilayer. The results indicate that the epilayer is a stoichiometric GaAs single crystal film.

Raman scattering measurements have been carried out on Si1-xGex/Si SLS. It is found that the Ge–Ge optic phonon frequency shift is proportional to strain in the SiGe film, and the Ge–Ge strain shift coefficient is 408cm−1. Based on these study a new method for analyzing the Raman spectra of SiGe/Si SLS has been proposed. Using the new method we can obtain the composition of the alloy sublayers as well as the strain in SLS. The strain distribution in the SiGe/Si SLS has been discussed, and strain in both SiGe and Si sublayers of the SLS have been calculated.

The small-pulse DLTS had been developed to measure distribution of deep levels in CVD grown SiGe/Si heterostructure before and after thermal processing at 800°C. Changes of defect states was found and after processing the original single deep level 0.62eV under the condition band split into two separated traps. A new weak deeper trap signal was found only in the just relaxed region. It could be Ge-related defect complex with misfit dislocations.

A rapid radiant heating, very low pressure CVD (RRH/VLP—CVD) has been successfully applied to GexSi1−x strained layer epitaxy on Si using SiH4' GeH4' B2H6 and PH3 as reaction gases at low temperature ranging from 550 to 650ĉ for operation pressure around mTorr. High quality GexSi1−x/Si strained layer heterostructure and superlattice were fabricated and high electrically active in—situ boron doping in GexSi1−x epilayer was also successfully achieved.