The silicon nanoporous pillar array （Si-NPA） is synthesized by using hydrothermal etching method, and the electron field emission properties are studied. The results show that Si-NPA has a low turn-on field of 1.48...The silicon nanoporous pillar array （Si-NPA） is synthesized by using hydrothermal etching method, and the electron field emission properties are studied. The results show that Si-NPA has a low turn-on field of 1.48 V/μm at the emission current of 0.1 μA and its field emission is relatively stable. The field emission enhancement of Si-NPA is believed to originate from its unique morphology and structure. Our finding demonstrates that the Si-NPA is a promising candidate material for field emission applications.展开更多
To understand the deformation and removal mechanism of material on nano-scale at ultralow loads,a systemic study on AFM micro/nano-machining on single crystal ailicon is conducted. The results indicate that AFM nano- ...To understand the deformation and removal mechanism of material on nano-scale at ultralow loads,a systemic study on AFM micro/nano-machining on single crystal ailicon is conducted. The results indicate that AFM nano- machining has a precisely dimensional controllability and a good surface quality on nanometer scale.A SEM is adopted to observe nano-machined region and chips,the results indicate that the material removal mechanisms change with the applied normal load. An XPS is used to analyze the changes of chemical composition inside and outside the nano-machined region respectively.The nano-indentation which is conducted with the same AFM diamond tip on the machined region shows a big discrepancy compared with that on the macro-scale. The calculated results show higher nano-hardness and elastic modulus than normal values .This phenomenon on be regarded as the indentation size effect(ISE).展开更多
Tip-enhanced Raman spectroscopy (TERS) has been used to obtain the Raman signal of surface species on silicon single crystal surfaces without the necessity for surface enhancement by addition of Ag nanoparticles. By i...Tip-enhanced Raman spectroscopy (TERS) has been used to obtain the Raman signal of surface species on silicon single crystal surfaces without the necessity for surface enhancement by addition of Ag nanoparticles. By illuminating the hydrogen terminated silicon surface covered with a droplet of 4-vinylpyridine with UV light, a 4-ethylpyridine modified silicon surface can be easily obtained. By bringing a scanning tunneling microscope (STM) Au tip with a nanoscale tip apex to a distance of ca. 1 nm from the modified silicon surface, enhanced Raman signals of the silicon phonon vibrations and the surface-bonded 4-ethylpyridine were obtained. The Raman enhancement factor was estimated to be close to 107. By comparing the surface enhanced Raman scattering (SERS) signal obtained after surface enhancement with Ag nanoparticles and the TERS signal of the surface, the advantage of TERS over SERS for characterizing the surface species on substrates becomes apparent: TERS readily affords vibrational information about the system without disturbing it by surface enhancement. In this sense, TERS can be considered a truly non-invasive tool which is ideal for characterizing the actual surface species on substrates.展开更多
Arrays of silicon micro\|tips were made by etching the p\|type (1 0 0) silicon wafers which had SiO 2 masks with alkaline solution. The density of the micro\|tips is 2×10 4 cm -2 . The Scanning Elect...Arrays of silicon micro\|tips were made by etching the p\|type (1 0 0) silicon wafers which had SiO 2 masks with alkaline solution. The density of the micro\|tips is 2×10 4 cm -2 . The Scanning Electron Microscope (SEM) photos showed that the tips in these arrays are uniform and orderly. The CN x thin film, with the thickness of 1.27μm was deposited on the silicon micro\|tip arrays by using the middle frequency magnetron sputtering technology. The SEM photos showed that the films on the tips are smoothly without particles. Keeping the sharpness of the tips will benefit the properties of field emission. The X\|ray photoelectron spectrum (XPS) showed that carbon, nitrogen and oxygen are the three major elements in the surfaces of the films. The percents of them are C: 69.5 %, N: 12.6 % and O: 17.9 %. The silicon arrays coated with CN x thin films had shown a good field emission characterization. The emission current intensity reached 3.2 mA/cm 2 at 32.8 V/μm, so it can be put into use. The result showed that the silicon arrays coated with CN x thin films are likely to be good field emission cathode. The preparation and the characterization of the samples were discussed in detail.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 10574112, and the Natural Science Foundation of Henan Province under Grant No 411011800.
文摘The silicon nanoporous pillar array （Si-NPA） is synthesized by using hydrothermal etching method, and the electron field emission properties are studied. The results show that Si-NPA has a low turn-on field of 1.48 V/μm at the emission current of 0.1 μA and its field emission is relatively stable. The field emission enhancement of Si-NPA is believed to originate from its unique morphology and structure. Our finding demonstrates that the Si-NPA is a promising candidate material for field emission applications.
基金This project is supported by National Natural ScienceFoundation of China (No.59835180) and Science andTechnology Foundatio
文摘To understand the deformation and removal mechanism of material on nano-scale at ultralow loads,a systemic study on AFM micro/nano-machining on single crystal ailicon is conducted. The results indicate that AFM nano- machining has a precisely dimensional controllability and a good surface quality on nanometer scale.A SEM is adopted to observe nano-machined region and chips,the results indicate that the material removal mechanisms change with the applied normal load. An XPS is used to analyze the changes of chemical composition inside and outside the nano-machined region respectively.The nano-indentation which is conducted with the same AFM diamond tip on the machined region shows a big discrepancy compared with that on the macro-scale. The calculated results show higher nano-hardness and elastic modulus than normal values .This phenomenon on be regarded as the indentation size effect(ISE).
基金supported by the National Natural Science Foundation of China (Grant Nos. 20673086, 20827003 and 20825313)the 973 Program(2009CB930703 and 2007CB935603)the Fok Ying Tung Foundation (101015)
文摘Tip-enhanced Raman spectroscopy (TERS) has been used to obtain the Raman signal of surface species on silicon single crystal surfaces without the necessity for surface enhancement by addition of Ag nanoparticles. By illuminating the hydrogen terminated silicon surface covered with a droplet of 4-vinylpyridine with UV light, a 4-ethylpyridine modified silicon surface can be easily obtained. By bringing a scanning tunneling microscope (STM) Au tip with a nanoscale tip apex to a distance of ca. 1 nm from the modified silicon surface, enhanced Raman signals of the silicon phonon vibrations and the surface-bonded 4-ethylpyridine were obtained. The Raman enhancement factor was estimated to be close to 107. By comparing the surface enhanced Raman scattering (SERS) signal obtained after surface enhancement with Ag nanoparticles and the TERS signal of the surface, the advantage of TERS over SERS for characterizing the surface species on substrates becomes apparent: TERS readily affords vibrational information about the system without disturbing it by surface enhancement. In this sense, TERS can be considered a truly non-invasive tool which is ideal for characterizing the actual surface species on substrates.
文摘Arrays of silicon micro\|tips were made by etching the p\|type (1 0 0) silicon wafers which had SiO 2 masks with alkaline solution. The density of the micro\|tips is 2×10 4 cm -2 . The Scanning Electron Microscope (SEM) photos showed that the tips in these arrays are uniform and orderly. The CN x thin film, with the thickness of 1.27μm was deposited on the silicon micro\|tip arrays by using the middle frequency magnetron sputtering technology. The SEM photos showed that the films on the tips are smoothly without particles. Keeping the sharpness of the tips will benefit the properties of field emission. The X\|ray photoelectron spectrum (XPS) showed that carbon, nitrogen and oxygen are the three major elements in the surfaces of the films. The percents of them are C: 69.5 %, N: 12.6 % and O: 17.9 %. The silicon arrays coated with CN x thin films had shown a good field emission characterization. The emission current intensity reached 3.2 mA/cm 2 at 32.8 V/μm, so it can be put into use. The result showed that the silicon arrays coated with CN x thin films are likely to be good field emission cathode. The preparation and the characterization of the samples were discussed in detail.
