【作者】 李瑞山；

【导师】 谢二庆；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2009， 博士

【摘要】 类金刚石碳(diamond-like carbon, DLC)是一类含有大量sp~3相碳的非晶亚稳碳材料的统称。DLC薄膜由于具有高硬度、化学稳定性、高光学透过率和比较宽的光学带隙,有非常广泛的应用前景,尤其是作为真空微电子器件的场发射阴极材料,近几年倍受关注。很多物理气相沉积(PVD)和化学气相沉积(CVD)方法都能制备DLC薄膜。但是气相制备方法难以实现大尺度沉积,并且成本较高,因此寻找一种低成本、可大尺度沉积的方法迫在眉睫。近几年Namba等人实践了液相电化学沉积DLC薄膜。与气相方法相比较,液相方法具有设备简单、成本低、实验温度低、实验易控制等特点。在研究者的努力下,液相电化学沉积DLC薄膜取得了很大的进展。本论文主要探索利用电化学方法制备DLC薄膜,并对其场发射性质进行研究,主要内容包括:1.常压下,在不同的直流电压下电解甲醇溶液在铝衬底表面制备DLC薄膜。利用SEM、FTIR、XPS和Raman光谱对薄膜的表面形貌和微结构进行了检测。随着沉积电压的上升,DLC薄膜中的sp~2相含量下降,且薄膜的表面形貌有显著地变化。这两个因素同时对DLC薄膜场发射性质产生影响,使DLC薄膜的场发射性质随沉积电压发生非单调变化。在1200V下沉积的DLC薄膜显示了最优的场发射性质。2.600V直流电压下,利用不同摩尔比的尿素/甲醇溶液为电解液在Si(100)表面沉积了不同氮含量的掺氮类金刚石(DLC:N)薄膜。XPS、FTIR和Raman检测显示氮元素与碳元素以C-N或C=N方式结合,并且氮元素的掺杂有利于薄膜中sp~2相的形成。对不同氮含量DLC:N薄膜场发射性质检测发现:场发射开启电场随着薄膜中氮含量的增加而降低,同时23.5 V/μm电场下场发射电流密度随着氮含量的增加而上升。氮含量增加对液相电沉积DLC:N薄膜场发射性质的提高是由于氮元素的施主电掺杂作用和薄膜中sp~2相的增加。3.在前面实验的基础上,利用简单的电化学装置,电解N,N-二甲基甲酰胺在衬底两面同时沉积了DLC薄膜。Raman检测显示铝衬底两面DLC薄膜不同位置的微结构高度相似,厚度分布在260-300nm。针对导电性衬底两面同时沉积DLC薄膜提出了一个简单的理论模型。铝衬底两面同时沉积DLC薄膜为在三维复杂结构衬底表面全方位沉积DLC薄膜提供了可能性。更多还原

【Abstract】 Diamond-like carbon (DLC) is a metastable form of amorphous carboncontaining a significant fraction of sp~3 bonds.It can have a high mechanical hardness,chemical inertness,optical transparency,and it is a wide band gap semiconductor.DLC films have widespread applications in many areas,especially as field emissioncathode materials for vacuum microelectronic devices.DLC films have been preparedby physical vapor deposition (PVD) or chemical vapor deposition (CVD).The aboveprocess is still questioned for its scalability and cost-effectiveness.Search forlow-cost and scalable technique for DLC deposition is still on the hot anvil.In recent times,possibility of depositing DLC films from organic liquids byelectrochemical technique was demonstrated by Namba.Electrodeposition techniquehas demonstrated some advantages over vapor phase deposition,such as thesimplicity and low cost of experimental apparatus,possibility of low temperaturesynthesis and ease of experimental control to produce films with diverse properties,etc.Subsequent efforts were devoted to the progress of electrodeposition of DLCfilms.The research work is concerned with the preparation of DLC films byelectrochemical deposition.The field electron emission properties of DLC films werealso investigated.The main research contents of this thesis are shown as follows:1.At ambient pressure,DLC films were deposited on Al substrates by electrolysis ina methanol solution under various voltages.The surface morphology andmicrostructure of the synthesized films were characterized by SEM,FTIR,XPSand Raman spectroscopy.With the increase of deposition voltage,the sp2 phaseconcentration decreased and the surface morphology changed dramatically.Theinfluence of deposition voltage on the field electron emission (FEE) properties ofDLC films was not monotonic due to two adverse effects of deposition voltage onthe surface morphology and compositions.The DLC film deposited under 1200 V exhibited optimum FEE property.2.Nitrogen incorporated diamond-like carbon (DLC:N) films with different Ncontent were deposited on Si(100) substrates by electrolysis of urea/methanolorganic solution with different mole ratios under a constant voltage of 600 V.Analysis by XPS,FTIR,and Raman spectrometry showed that N wasincorporated into the DLC films by sp~3 C-N and sp~2 C=N bonds and inducedgraphitization of the films.The influence of N content on the electronic fieldemission properties of these films was investigated.The turn-on field (Ec) waslowered with increasing N content,and there was a simultaneous rise in the fieldemission current densities under the electric field of 23.5 V/mm.Enhancement infield emission is attributed to the donor activity of nitrogen and the fieldenhancement effect of sp~2 clusters.3.On the basis of the investigation on deposition of DLC films in methanol,byelectrolysis of the N,N-dimethylformamide solution with simple electrochemicalapparatus,an attempt was made to simultaneously deposit DLC films on bothsurfaces of an aluminum Al substrate.Raman spectra showed that the structuresof the DLC film were uniform.The thickness distribution of the film was260-300 nm.A simple model of the sustaining mechanism was proposed forsimultaneous electrodeposition of the DLC film on both surfaces of conductivesubstrates.The simultaneous formation of the DLC film on both surfaces of theAl substrate showed a possibility in the three-dimensional deposition of DLCfilms on complex conductive substrates.更多还原