Novel ordered aloetic-shaped SiC nanowires were synthesized on a Si (100) substrate by reacting methane with silicon dioxide using iron as a catalyst. Their structure and chemical composition were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The wires have a tapered aloetic structure with a top diameter about 50-80 nm and a length about 10 microm. The field emission properties of the aloetic nanowires were investigated. A stable emission with current density of 0.525 mA/cm2 at an applied electric field of 2.2 V/microm and a low turn-on electric fields of 1.4 V/microm were observed. The excellent field emission properties indicate that the aloetic-shaped SiC nanowires may have potential applications in flat panel displays and electron field-emitting devices.

碳纳米管（CNT）和衬底的电学接触问题是获得高性能CNT电子器件的一个关键性的问题。本文采用电泳电镀方法制备CNT冷阴极,有效改善了CNT与衬底间接触电阻,增强了碳纳米管场发射性能。电泳电镀法制备的碳纳米管冷阴极场发射的开启电场（电流密度为10μA.cm-2时的电场）由2.95 V.μm-1降低到1.0V.μm-1,在电场为8V.μm-1时电流密度由0.224增加到0.8112mA.cm-2。在电流密度为800μA.cm-2时进行1h的场发射稳定性测试,结果表明,电泳电镀法所得CNT场发射电子源电流密度几乎不变,而且电流密度比较稳定;而只有电泳的方法获得的CNT场发射电子源电流密度波动较大,电流不稳定且呈较快的衰减趋势,1h后减少到原来的75%。采用电泳电镀方法制备CNT阴极,CNT的根部被纳米银颗粒覆盖和包裹,使CNT与衬底接触更加牢固而紧密,又由于银具有很好的导电性,从而大大减小了接触电阻,因此电泳电镀法能大大改善CNT与衬底的电学接触性能。

Using standard photolithography,patterned carbon nanotube line arrays were fabricated on silicon substrates by thermal chemical vapor deposition.Scanning electron microscopy and Raman spectroscopy were used to characterize the structure of the carbon nanotubes.The carbon nanotubes were very uniform and about 50 nm in diameter and 2 μm in length.The Raman spectrum showed that the carbon nanotubes were multi-walled carbon nanotubes.Field emission characteristics of the samples were characterized.It was found that the non-patterned carbon nanotube films,10 μm and 2 μm size carbon nanotube line arrays field emission characteristics were gradually improved with turn-on field of 3 V/μm,2.1 V/μm,1.7 V/μm and emission current density at applied electric field 3.67 V/m were 2.57 mA/cm2,4.65 mA/cm2,7.87 mA/cm2,respectively.The reasons may attribute to the field-screening effect and edge effect by analyzing the experimental results.

The variable-temperature photoluminescence spectra of strained InAsxP1-x/InP heterostructuer were experimentally determined in the temperature range 13~300 K.A theoretical calculation was presented that takes into account the temperature-induced variations in band gap and biaxial strain to explain the PL spectra.The results showed that strain which is induced by lattice mismatch between epitaxial layer and substrate removes the degeneracy between the light-and heavy-hole states at the top of the valence band,and with temperature under 100 K,the recombinations from the conduction band to the split valence bands are both observed in the photoluminescence spectra.As temperature is raised,it results in an increasingly larger light-hole population than that of heavy-hole due to thermalization,so when temperature is beyond 100 K only the recombination from the conduction band to the light-hole state can be observed.We also find that the energy of the recombination between the conduction band and the light-hole and heavy-hole state changes as a function of temperature.

The influence of interface barrier on field emission of carbon nanotubes (CNTs) was investigated theoretically and experimentally. A double-potential barrier model was proposed to calculate the electron tunneling probability through the interface and surface barriers. The calculation result reveals that the difference of the electron tunneling probability through the two barriers is responsible for the nonlinearity of the Fowler-Nordheim (FN) plots for the field emission of the CNTs. To verify this model, a series of the CNTs were synthesized on the Si substrates covered with different thicknesses of SiO2 layers as the interface barrier. Based on their field emission properties, it was found that the FN plots of the field emission of these CNTs deviated from the FN law when the applied electric fields were over a critical value, which was strongly dependent on the thicknesses of the SiO2 layer. Therefore, the interface barrier has an important role in determining the field emission property of the CNTs. The experimental results are consistent with the calculation result based on the double potential model.

An efficient carbon nanotubes(CNTs) field emission cathode has been successfully fabricated by combining electrophoresis and by electrochemical deposition technology.In fabrication,the silver patterns are deposited on an indium tin oxide glass by electrochemical method and then the CNTs are covered onto surface of the silver patterns by electrophoretic method.The cathode shows that excellent field emission characteristic,including a turn-on electric field of 2.8V/μm and an emission current density of 1.692mA/cm2 at an applied electric field of 5.5V/μm.The excellent field emission characteristic may be attributed to that surface electric field of CNTs are enhanced by edge and hills-like surface of silver pattern.The cathode is a promising candidate for large scale carbon nanotubes–based field emission display,due to its simple fabrication processes and excellent field emission characteristic.

Carbon nanotubes(CNTs)were deposited into planar and patterned indium tin oxide glass substrate with electrophoretic method as field emission cathode and theirs field emission characteristics were also investigated.Experimental results indicated that the field emission characteristic of the patterned CNT cathode was improved as compare with the planar CNT cathode.By calculating the electric field distribution,it was found that surface electric field of the patterned ITO electrode had an electric field enhancement resulting from the edge field effect.The improved field emission characteristic was attributed to two-grade field enhancement in surface of CNTs.In the fabrication of CNTs cathlode,it is an available way to enhance electron emission form CNTs that use of the patterned substrate electrode.