| Graphene is a single layer material consists of carbon atoms, and the carrier of which can move near the velocity of light. Thus graphene exhibits ultra-high carrier mobilities. CVD is the most industrialized production methods for graphene, but it faced a bottleneck that how transferred onto another substrate destructively and repeatedly. Electrochemical bubbling transfer is environmentally friendly, but there are still big damage, poor reproducibility of weakness. This paper systematically studied the mechanism proposed positive hydrogen ions and water penetration PMMA is mainly due to damage caused by graphene views and designs a new method of new air barrier, and she observed a certain quality and increase repeat improved.Graphene's good electrical properties have been utilized in graphene field-effect transistors(GFETs), which have broad application prospects in high-frequency circuits, detectors, etc. Growth of high-k dielectric layer on the graphene is very important for high-performance GFET. However, current processes of growing alumina film on graphene surface, such as atomic layer deposition, physical vapor deposition, etc., were not perfect, which introduced damages to graphene structure.Alumina has a good and stable physical and chemical properties, thus it has been applied in large scale in optoelectronics, solid state electronics, micro-electromechanical systems(MEMS) and so on. Conventional oxide film preparation methods require significant investment and complex equipment, which are difficult to control. In 1988, Nagayama first published the process of chemical liquid deposition(CLD) to grow silicon oxide film. In 2004, Sun et.al proposed a fluorin-free CLD process to grow alumina film on GaAs surface. After that, Basu succeeded in growing alumina film on GaN substrate using the CLD method. CLD process has various advantages, such as low investment, and good film uniformity. However, previous studies did not give clear evidence to elaborate CLD process mechanism.Details are as follows:1. Proposed a view that hydrogen ions and water pass through PMMA are main causes of graphene damages of conventional electrochemical bubbling transfer process;2. Achieved innovative results in graphene transfer process. the scheme of using polytetrafluoroethylene(PTFE) film as a stopping layer to avoid the water and H+ permeate PMMA has been designed. Compared with the scheme which only use polyethylene terephthalate(PET) frame as the graphene's support layer, the quality of graphene transferred by PTFE-assisted is better obviously, which was demonstrated by the result of Raman spectroscopy, SEM, AFM and electron mobility.3. Attempted to use CLD process to deposit Al2O3 on graphene. Observed the film with an optical microscope, and measured the conductivity. Experiment results the indicated that there's no Al(OH)3 groups attached to graphene surface, and CLD process is difficult to deposit aluminum oxide film on untreated graphene.4. Analyzed the particle size distribution of fresh growth solution, and observed the alumina film on the GaAs substrate with optical microscope and SEM. The results indicates that Al(OH)3 colloid has been formed in the growth solution, and CLD process is a physical absorption process of Al(OH)3 groups rather than ion chemical reaction process. |
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