热处理对纳米金刚石涂层场发射性能的影响(英文)

Influence of Thermal Annealing on Field Emission of Nano-diamond Coating

用旋涂法在金属钛衬底上涂敷纳米金刚石,经过适当的热处理形成金刚石涂层与金属钛衬底的化学键合,即形成衬底与涂层之间的过渡层,从而为纳米金刚石颗粒提供电子,使其成为有效的发射体。用扫描电镜、原子力显微镜、X射线衍射和拉曼散射等手段分析了温度对键合效果以及场发射性能的影响,温度过高或过低都不利于提高纳米金刚石涂层的场发射性能,只有在700℃左右对样品进行热处理,才能得到较好的键合状态。改变涂膜时旋涂的次数以获得不同涂层厚度的样品,对其在700℃的相同温度下进行热处理,发现涂层过厚或过薄都不利于样品发射性能的提高。旋涂9次并于700℃热处理的样品具有较好的场发射性能,其发射阈值场强可达4.6V/μm,而15.3V/μm场强下的电流密度为59.7μA/cm2。

The fabricating processes of diamond-based field emission cathode mainly include two modes： growing film and fabricating micro tips or micro-patterned emitters. Growing film is time-consuming and ineffective; micro pattern fabricating is cost-consuming and complicated. Both processes are not adapted to commercial application of large screen field emission displays. The third process was supposed in this paper：coating nano-diamond powders on titanium substrate by spin-coating method. Ohmic contact between diamond coating and Ti substrate could be formed after thermal annealing at proper temperature, which supplies electrons for nano-diamond particles located in coating surface and make them effective emitters. Atomic force microscopy （ AFM ）, scanning electron microscopy （ SEM ）, X-ray diffraction （ XRD ） and Raman spectroscopy were employed to study the influence of the annealing temperature on bonding effect and field emission properties. Thermal treatment at extreme low or high temperature is not benefit to improve the field emission properties of the samples, while the ones annealed at about 700 ℃ could gain better bonding state. The samples with different coating thickness were annealed at 700 ℃ to investigate the effect of the coating thickness on the field emission property. Taking the electron transport and diamond emitter number into considerations, neither the excessive thick nor thin coating is good for amelioration of the emission property. Annealed at 700 ℃, the sample with nine-layer coating presents better property. The threshold electric field of the sample is 4.6 V/μm, and the current density can reach to 59.7 μA/cm^2 at 15.3 V/μm.