- 學位論文
一維次微米鑽石柱之場發射特性研究
Field emission from one-dimensional submicron diamond rods
摘要
本研究利用氧氣電漿和化學液蝕刻HFCVD摻錋多晶鑽石，成功的開發出高場發射電流密度35mA/cm2 (at 8.5 V/μm)和低啟動電場4.3 V/μm ( at 10 μA/cm2)的一維次微米鑽石柱林。實驗利用RF射頻13.56 MHz的氧氣電漿系統，功率100W下進行不同時間，不同腔體壓力和不同偏壓大小的蝕刻。最後利用其中最佳參數(壓力15mtorr、功率100W、偏壓-1300V、時間6小時蝕刻的試片再以氯化氫液(HCl37%)在温度90℃下進行30分鐘的溼式蝕刻，接著以銅電極間距100μm、壓力10-6 torr 真空下量測場發射特性。 實驗結果顯示，隨著氧電漿蝕刻時間的增加，鑽石柱林之長度隨著變長，場發射性質因而得到改善。當提升電漿自行偏壓由-1000V到-1300V時，鑽石柱林長度(直徑)由4.2μm（420 nm）變為4.8μm（370 nm），場發射性質也得到改善。接著利用氯化氫液將鑽石柱表面因不鏽鋼生成的Fe2O3蝕刻清除後，鑽石由柱狀變為尖部呈細絲的錐狀，場發性質得到顯著提升，在相同電場8.5 V/μm下場發電流密度由1 mA/cm2提升到35mA/cm2，啟動電場自6 V/μm降至4.3 V/μm ( at 10 μA/cm2)。場發射穩定度方面，一開始出現一穩定區，之後電流密度隨時間快速下降，最終趨於飽和。隨著初始電流密度的增加，穩定區的生命期變短，施加電場越大者表現出越快達到飽和的現象。
並列摘要
One-dimensional boron-doped sub-micron diamond rods (SDRs) with excellent field emission current density 35mA/cm2 (at 8.5 V/μm) and turn on field 4.3 V/μm ( at 10 μA/cm2)are fabricated on polycrystalline diamond/Si by oxygen plasma etching and subsequent HCl etching. SDRs are fabricated on the polycrystalline diamond/Si substrate, made from HFCVD, by using oxygen plasma etching in capacitance coupled plasma (CCP) chamber operated at a radio frequency (RF) of 13.56 MHz. The RF power source is operated at 100 W. The total oxygen gas pressure is kept at 15 mtorr and the self-bias voltage is -1300 V during etching. The one-dimensional SDRs are further wet-etched by HCl(37%) at 90℃for 30 minutes. Field emission properties are measured at 10-6 torr with a spacing of 100μm between the copper anode and cathode. Experimental results indicate that field emission characteristics are better for longer SDRs. The SDRs’ length (diameter) change from 4.2μm (420nm) to 4.8μm (370nm) as the plasma self-bias voltage increase from -1000V to -1300V, associate with better field emission characteristics. Nevertheless, the as-etched SDRs suffer with high turn-on field (ETO) and low field emission current density (JFE) due to residual iron oxide on the rods’ surfaces. A huge improvement in the field emission characteristics can be achieved by removing iron oxide using a wet-etch process in a diluted HCl (37%). After the wet-etch, field emission current density (JFE) increases from 1 mA/cm2 to 35mA/cm2 under the same filed 8.5 V/μm and turn-on field (ETO) reduces from 6V/μm to 4.3 V/μm ( at 10 μA/cm2). Stability test shows a stable period exists in the beginning and after that the current density decay significantly and approach saturation at last. The stable period become smaller and the near saturation time become shorter with increasing applied field.