HfO2的纯度对紫外多层膜反射率的影响

用辉光放电质谱法和二次离子质谱仪测定了两种HfO2材料及它们相应的单层膜中的杂质含量，结果发现，无论是在体材料中还是在用电子束蒸发技术沉积的材料单层薄膜中，ZrO2都是这两种HfO2材料中最主要的杂质。而且，这两种HfO2材料中Zr含量的差别远远大于Ti、Fe含量的差别，这说明Zr含量的差别正是引起两种HfO2膜层光学性能差别的原因。用这两种不同纯度的HfO2材料与同一纯度的SiO2材料组合，沉积形成266nm的紫外反射镜，实验结果表明这两种反射镜的反射率分别在99.85% 和 99.15%左右。这个结果与依据单层膜得出的光学常数所设计的结果符合的很好。

Investigation on thermal stability of TiO2 films for application at high temperature

The thermal stability of electron beam deposited TiO2 monolayers and TiO2/SiO2 high reflectors (HR) during 300 to 1100 degrees C annealing is studied. It is found that the optical loss of film increases with the increase in annealing temperature, due to the phase change, crystallisation and deoxidising of film. Scattering loss dominates the optical property degradation of film below 900 degrees C, while the absorption is another factor at 1100 degrees C. The increase in refractive index and decrease in physical thickness of TiO2 layer shift the spectra of HR above 900 degrees C. The possible crack mechanism on the surface of HR during annealing is discussed. Guidance for application on high temperature stable optical coatings is given.

Field emission vacuum power switch using vertically aligned carbon nanotubes

The best field emission properties from carbon nanotube cathodes were obtained when their heights, diameters and spacings were optimized. Field emission currents as high as 10 mA were obtained from 1 cm × 1 cm vertically aligned CNT cathode with optimized parameters grown using dc plasma CVD in situ. It was found that in order to obtain large emission current of >10 mA, space charge effects within the electron beam must be taken into account.

GHz modulation of carbon nanotube cathodes for microwave amplifiers

Cold cathodes based on carbon nanotubes (CNs) allow to produce a pulsed/directly modulated electron beam. Using an array of vertically aligned CNs that exhibit an aspect ratio of around 200, we demonstrated the modulation of a 1.5 A/cm2 beam at 1.5 GHz frequency. Such CN cathodes are very promising for their use in a new generation of compact and low cost microwave amplifiers that operates between 30 and 100 GHz. ©2005 IEEE.

Transparent liquid-crystal-based microlens array using vertically aligned carbon nanofiber electrodes on quartz substrates.

A novel transparent liquid-crystal-based microlens array has been fabricated using an array of vertically aligned multi-wall carbon nanofibers (MWCNFs) on a quartz substrate and its optical characteristics investigated. Electron beam lithography was used for the catalyst patterning on a quartz substrate to grow the MWCNF array of electrodes. The structure of the electrode array was determined through simulation to achieve the best optical performance. Both the patterned catalyst and growth parameters were optimized for optimal MWCNF properties. We report an in-depth optical characterization of these reconfigurable hybrid liquid crystal and nanofiber microlens arrays.

Selective epitaxial growth in silicon on insulator: Planarity and mass flow

Seeded zone-melt recrystallization using a dual electron beam system has been performed on silicon-on-insulator material, which was prepared with single-crystal silicon filling of the seed windows by selective epitaxial growth. The crystal quality has been assessed by a variety of microscopic techniques, and it is shown that single-crystal films 0.5-1.0 μm thick over 1.0 μm of isolating oxide may be prepared by this method. These films have considerably less lateral variation in thickness than standard material, in which the windows are not so filled. The filling method is suitable for both single- and multiple-layer silicon-on-insulator, and gives the advantages of excellent layer uniformity after recrystallization and improved planarity of the whole chip structure. Experiments using various amounts of seed window filling have shown that the lateral variations of silicon film thickness seen in unplanarized material are due to stress relief in the cap oxide when the silicon film is molten, rather than the effect previously postulated in which they were assumed to be due to the contraction of silicon on melting.

An automatic focusing and stigmating system for the SEM

A digital minicomputer has been interfaced with a scanning electron microscope, and programmed to control the excitations of the objective lens and the stigmator of the microscope. The electron beam is scanned by a digital scan generator and the digitised video signal is used for computations. To focus the microscope, a parameter related to the 'sharpness' of the image is maximised, and to set the stigmator, the directional information in the above- and below-focus images is used. | A digital minicomputer has been interfaced with a scanning electron microscope, and programmed to control the excitations of the objective lens and the stigmator of the microscope. The electron beam is scanned by a digital scan generator and the digitized video signal is used for computations. To focus the microscope, a parameter related to the 'sharpness' of the image is maximized, and to set the stigmator, the directional information in the above and below-focus images is used.

REGROWTH RATES OF AMORPHOUS LAYERS IN SILICON-ON-SAPPHIRE FILMS.

The rate and direction of regrowth of amorphous layers, created by self-implantation, in silicon-on-sapphire (SOS) have been studied using time resolved reflectivity (TRR) experiments performed simultaneously at two wavelengths. Regrowth of an amorphous layer towards the surface was observed in specimens implanted with 3 multiplied by (times) 10**1**5Si** plus /cm**2 at 50keV and regrowth of a buried amorphous layer, from a surface seed towards the sapphire, was observed in specimens implanted with 1 multiplied by (times) 10**1**5Si** plus /cm**2 at 175keV. Rapid isothermal heating to regrow the layers was performed in an electron beam annealing system. The combination of 514. 5nm and 632. 8nm wavelengths was found to be particularly useful for TRR studies since the high absorption in amorphous silicon, at the shorter wavelength, means that the TRR trace is not complicated by reflection from the silicon-sapphire interface until regrowth is nearly complete.

RESIDUAL DEFECTS FOLLOWING RAPID ANNEALING OF BORON IMPLANTED SILICON WITH AND WITHOUT PREAMORPHISATION BY SILICON IMPLANTATION.

Implants of boron into silicon which has been made amorphous by silicon implantation have a shallower depth profile than the same implants into silicon. This results in higher activation and restricted diffusion of the B implants after annealing, and there are also significant differences in the microstructure after annealing compared with B implants into silicon. Rapid isothermal heating with an electron beam and furnace treatments are used to characterize the defect structure as a function of time and temperature. Defects are seen to influence the diffusion of non-substitutional boron.

Carbon nanotube based cathodes for microwave amplifiers

We have studied two different kinds of electron tubes using a cold field emission cathode as the electron source. This cathode is an array of vertically aligned multiwall carbon nanotubes. The first device is a triode. With this device, we demonstrated the modulation at 32 GHZ of a 1.4 A/cm2 peak current density with a 82% modulation ratio. The second device is a traveling wave tube. For this device, the objective is to test a cathode delivering a 2 A/cm 2 electron beam. ©2009 IEEE.

Angular distribution of field emitted electrons from vertically aligned carbon nanotube arrays

Angular field emission (FE) properties of vertically aligned carbon nanotube arrays have been measured on samples grown by plasma enhanced chemical vapor deposition and characterized by scanning electron microscope and I-V measurements. These properties determine the angular divergence of electron beams, a crucial parameter in order to obtain high brilliance FE based cathodes. From angular distributions of the electron beam transmitted through extraction grids of different mesh size and by using ray-tracing simulations, the maximum emission angle from carbon nanotube tips has been determined to be about ± 30 around the tube main axis. © 2012 American Institute of Physics.

High-performance nanowire oxide photo-thin film transistor.

A gate-modulated nanowire oxide photosensor is fabricated by electron-beam lithography and conventional dry etch processing.. The device characteristics are good, including endurance of up to 10(6) test cycles, and gate-pulse excitation is used to remove persistent photoconductivity. The viability of nanowire oxide phototransistors for high speed and high resolution applications is demonstrated, thus potentially expanding the scope of exploitation of touch-free interactive displays.

Experimental investigation on submicron rib waveguide microring/racetrack resonators in silicon-on-insulator

in experiment, characteristics of silicon microring/racetrack resonators in submicron rib waveguides have been systematically investigated. It is demonstrated that only a transverse-electric mode is guided for a ratio of slab height to rib height h/H = 0.5. Thus, these microring/racetrack resonators can only function for quasi-transverse-electric mode, while they get rid of transverse-magnetic polarization. Electron beam lithography and inductively coupled plasma etching were employed and improved to reduce side-wall roughness for low propagation loss and high performance resonators. Then, the effects of waveguide dimensions, coupling region design, waveguide roughness, and oxide cladding for the resonators have been considered and analyzed. (C) 2008 Elsevier B.V. All rights reserved.

Photoelectric characteristics of metal/InGaN/GaN heterojunction structure

A heterojunction structure photodetector was fabricated by evaporating a semitransparent Ni/Au metal film oil the InGaN/GaN structure. The photocurrent (PC) spectra show that both the Schottky junction (NiAu/InGaN) and the InGaN/GaN isotype heterojunction contribute to the PC signal which suggests that two junctions are connected in series and result in a broader spectral response of the device. Secondary electron, cathodoluminescence and electron-beam-induced current images measured from the same area of the edge surface clearly reveal the profile of the layer structure and distribution of the built-in electric field around the two junctions. A band diagram of the device is drawn based oil the consideration of the polarization effect at the InGaN/GaN interface. The analysis is consistent with the physical mechanism of a tandem structure of two junctions connected in series.

Design, fabrication and characterization of a high-performance microring resonator in silicon-on-insulator

A high-performance microring resonator in a silicon-on-insulator rib waveguide is realized by using the electron beam lithography followed by inductively coupled plasma etching. The design and the experimental realization of this device are presented in detail. In addition to improving relevant processes to minimize propagation loss, the coupling efficiency between the ring and the bus is carefully chosen to approach a critical coupling for high performance operating. We have measured a quality factor of 21,200 and an extinction ratio of 12.5dB at a resonant wavelength of 1549.32nm. Meanwhile, a low propagation loss of 0.89dB/mm in a curved waveguide with a bending radius of 40 mu m is demonstrated as well.