Thermal oxidation of SiAlON powders synthesized from coal gangue

The oxidation behavior of different SiAlON phases（β-SiAlON,X-phase SiAlON and 12H powders） synthesized from coal gangue in air atmosphere was investigated using isothermal thermogravimetry（TG） and field-emission scanning electron microscopy（FE-SEM）.The effect of ferric oxide impurities in coal gangue was studied.The results show that ferric oxide contributes to the growth of SiAlON crystalline during the synthesis process.In the oxidation experiment,the existence of ferric oxide decreases the oxidation resistance of SiAlON.The reason is that the impurity causes the formation of a liquid phase at a higher temperature.At 1423-1623 K,the oxidation of SiAlON powders is diffusion controlled and it can be described by Chou＇s model.A fair agreement is found between theoretical calculations and the experimental data.

Evolution of stress in evaporated silicon dioxide thin films

The evolution of stress in evaporated SiO2, used as optical coatings, is investigated experimentally through in situ stress measurement. A typical evolution pattern consisting of five subprocedures （thin film deposition, stopping deposition, cooling, venting the vacuum chamber, and exposing coated optics to the atmosphere） is put forward. Further investigations into the subprocedures reveal their features. During the deposition stage, the stresses are usually compressive and reach a stable state when the deposited film is thicker than 100 nm. An increment of compressive stress value is observed with the decrease of residual gas pressure or deposition rate. A very low stress of-20 MPa is formed in SiO2 films deposited at 3×10^-2 Pa. After deposition, the stress increases slightly in the compressive direction and is subject to the stabilization in subsequent tens of minutes. In the process of venting and exposure, the compressive component increases rapidly with the admission of room air and then reaches saturation, followed by a logarithmic decrement of the compressive state in the succeeding hours. An initial discussion of these behaviors is given.

Low threshold voltage light-emitting diode in silicon-based standard CMOS technology

Low-voltage silicon （Si）-based light-emitting diode （LED） is designed based on the former research of LED in Si-based standard complementary metal oxide semiconductor （CMOS） technology. The low-voltage LED is designed under the research of cross-finger structure LEDs and sophisticated structure enhanced LEDs for high efficiency and stable light source of monolithic chip integration. The device size of low-voltage LED is 45.85x38.4 （#m）, threshold voltage is 2.2 V in common condition, and temperature is 27 ~C. The external quantum efficiency is about 10-6 at stable operating state of 5 V and 177 mA.

Silicon electro-optic modulator with high-permittivity gate dielectric layer

A high-permittivity （high-k） material is applied as the gate dielectric layer in a silicon metal-oxide- semiconductor （MOS） capacitor to form a special electro-optic （EO） modulator. Both induced charge density and modulation efficiency in the proposed modulator are improved due to the special structure design and the application of the high-k material. The device has an ultra-compact dimension of 691 μm in length.

Thermal stress cleaving of silicon wafer by pulsed Nd:YAG laser

The applied laser energy absorbed in a local area in laser thermal stress cleaving of brittle materials using a controlled fracture technique produces tensile thermal stress that causes the material to separate along the moving direction of the laser beam. The material separation is similar to crack extension, but the fracture growth is controllable. Using heat transfer theory, we establish a three-dimensional （3D） mathematical thermoelastic calculational model containing a pre-existing crack for a two-point pulsed Nd：YAG laser cleaving silicon wafer. The temperature field and thermal stress field in the silicon wafer are obtained by using the finite element method （FEM）. The distribution of the tensile stress and changes in stress intensity factor around the crack tip are analyzed during the pulse duration. Meanwhile, the mechanism of crack propagation is investigated by analyzing the development of the thermal stress field during the cleaving process.

A DFT study of two-dimensional P_2Si monolayer modified by single transition metal(Sc-Cu)atoms for efficient electrocatalytic CO_(2)reduction

In the present work,a stable two-dimensional(2D)P_(2)Si monolayer was predicted.The monolayer is semimetallic/metallic under the PBE/HSE06 functional and is mechanically isotropic.The stability of the P_(2)Si monolayer has been proved via cohesive energy,mechanical criteria,molecular dynamics simulation,and phonon dispersion respectively,and the monolayer possesses high carrier mobility which is three times that of Mo S_(2).On the other hand,the catalytic performance of the P_(2)Si monolayer modified with a single transition metals(M=Sc-Cu)atom for the electrochemical reduction of CO_(2)was investigated,and the monolayer can catalyze CO_(2)with three constraints:stable molecular dynamics,high migration potential of metal atoms,and suitable band gap for electrocatalyst after metal doping exhibiting excellent catalytic stabilization activity and CRR selectivity.In addition,the reduction product of V@P_(2)Si is HCOOH with an overpotential as low as 0.75 V,and the most suitable reaction path is^(*)CO_(2)→^(*)CHOO→O^(*)CHOH→^(*)+HCOOH with the final reduction product HCOOH obtained.As a whole,the above results endow the P_(2)Si monolayer to be a good 2D material holding great promises for applications in nanoelectronics and CO_(2)reduction catalysts.

Effect of oxygen flow rate on the properties of SiO_x films deposited by reactive magnetron sputtering

SiOx （x = 0-2） films were deposited on BK-7 substrates by a low frequency reactive magnetron sputtering system with the oxygen flow rate （OFR） changing from 0 to 30 sccm. The samples were characterized by atomic force microscopy, spectrophotometer, and X-ray photoelectron spectroscopy. The extinction coefficient and refractive index decrease, while the optical transmittance increases with the increase of OFR from 0 to 17 sccm. The root mean square surface roughness has a maximum at 10 sccm OFR. The highest deposition rate is at 15 sccm OFR. Our results show that the films deposited at 20 sccm OFR are stoichiometric silica with relatively high deposition rate, low extinction coefficient, and low surface roughness. Therefore, a precise control of OFR is very important to obtain high quality films for optical applications.

Analysis of laser induced thermal mechanical relationship of HfO_2/SiO_2 high reflective optical thin film at 1064 nm

A numerical model is developed for the calculation of transient temperature field of thin film coating induced by a long-pulsed high power laser beam. The electric field intensity distribution of HfO2/Si02 high reflective （HR） film is investigated to calculate the thermal field of the film. The thermal-mechanical relationships are discussed to predict the laser damage area of optical thin film under long pulse high energy laser irradiation.

Design of guided mode resonant filters for authentication applications through azimuthal angles varying

Guided mode resonant filters （GMRFs） for authentication application with low sideband reflection at 0^o and 90^o azimuthal angles were designed. Using rigorous coupled-wave analysis, the diffractive characteristics of this kind device with different illumination angles, groove depths, and thicknesses of cover SiO2 layer were investigated. The structure of GMRF which satisfies the requirements for authentication applications was obtained. Illuminated at 30^o for a definite polarization mode, the filter presents symmetrical reflectance shape, low sideband reflectance, two separate reflectance peaks, and definite full-width at halfmaximum （FWHM） at 0^o and 90^o azimuthal angles.

Enhanced laser induced damage threshold of dielectric antireflection coatings by the introduction of one interfacial layer

A new method for increasing laser induced damage threshold （LIDT） of dielectric antireflection （AR） coating is proposed. Compared with AR film stack of H2.5L （H：HfO2, L：SiO2） on BK7 substrate, SiO2 interracial layer with four quarter wavelength optical thickness （QWOT） is deposited on the substrate before the preparation of H2.5L film. It is found that the introduction of SiO2 interfacial layer with a certain thickness is effective and flexible to increase the LIDT of dielectric AR coatings. The measured LIDT is enhanced by about 50%, while remaining the low reflectivity with less than 0.09% at the center wavelength of 1064 nm. Detailed mechanisms of the LIDT enhancement are discussed.

Contamination process and laser-induced damage of HfO_2/SiO_2 coatings in vacuum

The performances of HfO2/SiO2 single- and multi-layer coatings in vacuum influenced by contamination are studied. The surface morphology, the transmittance spectrum, and the laser-induced damage threshold are investigated. The results show that the contamination in vacuum mainly comes from the vacuum system and the contamination process is different for the HfO2 and SiO2 films. The laser-induced damage experiments at 1064 nm in vacuum show that the damage resistance of the coatings will decrease largely due to the organic contamination.

Nondestructive identification of ancient Chinese glasses by Raman and proton-induced X-ray emission spectroscopy

Nondestructive Raman spectroscopy and external-beam proton-induced X-ray emission （PIXE） technique to analyze eight ancient glasses unearthed from the provinces of Henan,Hubei,and Jiangsu,which allowes for a good characterization of the glass matrix and chemical compositions,is carried out.The results indicate that all the eight glass samples could be typically divided into three systems： faience （sample No.SZWG-4）,PbO-BaO-SiO 2 （sample Nos.NYWKI-5-1,HNWKII-88,and HNWKII-84）,and Na 2 OCaO-SiO 2 （sample Nos.HBWKI-16,HBWKI-17,HBWKI-18,and SZWG-1）.Additional relationships between the Raman spectra and parameters,such as residues of raw materials and opacifying agent,are also discussed by respectively comparing them with similar glass samples excavated from other historical sites.

Laser-conditioning mechanism of ZrO_2/SiO_2 HR films with fitting damage probability curves of laser-induced damage

The method of fitting damage probability curves of laser-induced damage is introduced to investigate the laser-conditioning mechanism of ZrO2/SiO2 high reflection（HR） films.The laser-induced damage thresholds（LIDTs） of the sample are tested before and after the laser-conditioning scanning process.The parameters of the defects are obtained through the fitting process of the damage probability curve.It can be concluded that the roles of laser conditioning include two aspects：removing defects with lower threshold and producing new defects with higher threshold.The effect of laser conditioning is dependent on the competition of these two aspects.

Comparison of laser-induced damage in Ta_2O_5 and Nb_2O_5 single-layer films and high reflectors

Ta2O5 and Nb2O5 films are deposited on BK7 glass substrates using an electron beam evaporation method and are annealed at 673 K in the air. In this letter, comparative studies of the optical transmittance, microstructure, chemical composition, optical absorption, and laser-induced damage threshold （LIDT） of the two films are conducted. Findings indicate that the substoichiometric defect is very harmful to the laser damage resistance of Ta2O5 and Nb2O5 films. The decrease of absorption improves the LIDT in films deposited by the same material. However, although the absorption of the Ta2O5 single layer is less than that of the Nb2O5 single layer, the LIDT of the former is lower than that of the latter. High-reflective （HR） coatings have a higher LIDT than single layers due to the thermal dissipation of the SiO2 layers and the decreased electric field intensity （EFI）. In addition, the Nb2O5 HR coating achieves the highest LIDT at 25.6 J/cm^2 in both single layers and HR coatings.

Biocompatible and stable core/shell drug nanocarrier with high surface-enhanced Raman scattering activity

A novel drug carrier based on SiO_2-coated silver nanoparticle aggregates and antitumor drug is successfully synthesized.The surface-enhanced Raman scattering（SERS） spectra of the antitumor drug in living cells are obtained.By using silver nano-aggregates as SERS substrates instead of dispersed silver particles, a great improvement of SERS signal intensity is achieved.It is found that the chemical stability of the drug carrier can also be increased with the existence of SiO_2 shell.The adsorbing effect between antitumor drug 9-aminoacridine（9AA） and silver particles is investigated to optimize the SERS signal. The core/shell structure of the drug carrier is characterized by ultraviolet-visible（UV-Vis） spectroscopy and transmission electron microscopy（TEM） pictures.The experimental results show that the drug carrier offers biocompatibility,stability,and high SERS activity,holding the potential for realizing the intracellular drug tracing.

Influence of APS bias voltage on properties of HfO_2 and SiO_2 single layer deposited by plasma ion-assisted deposition

HfO2 and SiO2 single layer is deposited on glass substrate with plasma ion assistance provided by Leybold advanced plasma source （APS）. The deposition is performed with a bias voltage in the range of 70-130 V for HfO2, and 70-170 V for SiO2. Optical, structural, mechanical properties, as well as absorption and laser induced damage threshold at 1064 nm of HfO2 and SiO2 single layer deposited with the plasma ion assistance are systematically investigated. With the increase of APS bias voltage, coatings with higher refractive index, reduced surface roughness, and higher laser-induced damage threshold （LIDT） are obtained, and no significant change of the absorption at 1064 nm is observed. For HfO2, a bias voltage can be identified to achieve coatings without any stress. However, too-high bias voltage can cause the increase of surface roughness and stress, and decrease the LIDT. The bias voltage can be properly identified to achieve coatings with desired properties.

20-kHz watt-level green laser with LGS crystal electro-optic Q-switch

A diode-end-pumped electro-optic （EO） Q-switched green laser operating at the repetition rate of 20 kHz is reported. A block of La3Ga5SiO14 （LGS） single crystal is used as a Q-switch and the type I phase- matching LiB305 （LBO） is used as the nonlinear crystal in the second harmonic generation. The 2.3-W average power of 532-nm green laser is obtained at the repetition rate of 20 kHz with the pulse width as short as 10 us. When the output power is about 1.5 W, the measured power fluctuation is less than 1.4% （root-mean-square. RMS） with the beam quality factor of M^2 〈 2 in both orthogonal directions.

Accurate analysis of ellipsometric data for thick transparent films

Using e-beam evaporation, the ellipsometric parameters of thick transparent films are studied with the modified analysis method for the SiO 2 film samples deposited onto the Si substrate. The ellipsometric parameters are measured at the incidence angles changing from 50 to 70 and in the 3–4.5 eV photon energy range. The error in the conventional method can be significantly reduced by the modified ellipsometric method considering the spatial effect to show good agreement between the theoretical and experimental results. The new method presented in this letter can be applied to other optical measurement of the periodic or non-periodic film structures.

Design of LICVD equipment for preparation of nano powder and study on laser threshold

A laser-induced chemical vapor deposition (LICVD) nanometer equipment is designed and fabricated. The design conception of key parts is expatiated. The energy threshold of SiH4 decomposing is studied. In the condition of same reactive gas flux, the laser energy threshold decreases with the increase of SiH4 concentration. In the condition of same SiH4 concentration, with the increase of reactive gas flux, the laser energy threshold which induces SiH4 decomposition increases linearly at the beginning, and when the flux is more than 100 ml/min, it turns to increase slowly. The factors which influence the laser threshold are analyzed.

Optical humidity-sensitive mechanism based on refractive index variation

A novel composite model is put forward for humidity-sensitive material based on Maxwell-Garnett and effective medium theory. The analytical expression of the relation between effective refractive index and relative humidity is shown with different absorption factors and porosities. The larger the absorption factor is, the higher the refractive index is. The refractive index of humidity-sensitive SiO2 film decreases with the increase of ceramic material porosity. The sensitivity of optical humidity sensor can reach the magnitude of 10-3. In comparison with the experimental humidity-sensing curve by the method of p-polarized reflectance and the analysis of mechanism, theoretical simulation is in agreement with experimental results. Therefore, this composite model is proved to be reasonable which lays new theoretical foundation in further research on optical humidity sensor.