Selective Growth of ZnO Nanorods on Si and the Application of Field Emission Device
|關鍵字:||氧化鋅;奈米柱;場發射;選擇性成長;異質接面;ZnO;nanorod;field emission;selective growth;heterojunction|
最後，我們利用鍍金探針的AFM和SCM量測單根氧化鋅奈米柱的電性。從I-V結果中可知氧化鋅和金的蕭基能障是0.34eV，介面理想因子是11，可能原因是接觸電阻太大與後面串聯一異質介面的電阻。而氧化鋅和矽的異直接面中，導帶差異為0.3 eV，內建電壓為0.48eV，此值比理想值略為下降的原因是由於介面能階的存在。總體而言，單根氧化鋅奈米柱用於場發射元件的頻率響應分為蕭基介面和異質介面，它們分別是MHz和GHz 的速度。|
In this thesis, we produced the patterned ZnO nanowires and its field emission device (FED) properties were also studied. Finally, the junction characteristics of one single ZnO nanorod with Au and Si substrate were investigated. The PS surface provides a rough surface morphology, Zn vapor might condense easily on the PS surface and forms a wetting layer, but not on the flat Si surface., to form a wetting layer by decreasing the surface energy so that ZnO nanowires can grow without any catalyst. The rough morphology of a PS surface was proven advantageous for the growth of nanowires by reducing its strain and increasing the number of nuclei sites. The probable growth mechanism should be the vapor-solid (VS) process. Moreover, Site-specific nanorods of ZnO were grown at low temperature by Plasma Enhanced Chemical Vapor Deposition (PECVD). The selective growth of ZnO nanorods at a relatively low growth temperature suggests that it can be integrated on device platforms for nanoelectronics. In addition, this technique also gives advantages of controlling the growth site and varying the proper interrod distance as well as the emitter density while growing the ZnO nanorods. A field emission experiment for such patterned ZnO nanorods was conducted to indicate the F-N tunneling model. Sample of medium density is shown a better field enhancement factor than that of higher density. Therefore, uniformly distributed the nanorods with a medium density by site-specific growth is thus clearly required and this approach was demonstrated the possibility of the integration of FE nanodevices by one-dimensional ZnO nanorods on a silicon substrate. Besides, blue light might result from the exciton emission or the defect level emission in the FE experiments proved that the blue emission corresponds to the electron transition from the shallow donor level of oxygen vacancy and zinc interstitials to the valence band. ZnO nanowires are the promising candidate for UV and blue light emitter. On the other hand, integrated Field Emission (FE) experiments were performed and involved the F-N tunneling mechanism. Nonlinearity of Fowler–Nordheim (FN) plot was observed under FE in local area. The relation between FE phenomena and defect amount of ZnO nanorods were studied. The phenomena can be explained by the adsorbate effects.and we found that the slope change had proportion to the amount of work function difference. The oxygen defects in ZnO nanorods might easily cause adsorption to lower fork function which decreased the slope of FN plots and hence affect the FE properties. Finally, we measured the electric properties of single ZnO nanorod by conductive AFM and SCM. From those measurements, the schottky barrier height was about 0.34 eV and the ideal factor was about 11 due to the contact resistance and series connection of resistance from ZnO nanorod. The of heterojunction was also about 0.3 eV and the built-in voltage was about 0.48 eV below the ideal contact resulting from the interface state existing. For the application of FED, the frequency response of the two junctions, on -1~0 V is for schottky junction and 0-1 V is for heterojunction. They are MHz and GHz, respectively.
|Appears in Collections:||Thesis|