pH值誘發自組裝單根鑽石奈米線之電性與電子傳輸行為研究

Abstract

摘要 利用分子間氫鍵的作用力使奈米鑽石在不同pH值的磷酸鹽生理食鹽水相互連結形成長約3-10 m、直徑約300-1200 nm的鑽石奈米線，為了更加瞭解這種分子自組裝合成的鑽石奈米線基本電性，我們將單根鑽石奈米線製作成元件以便進行量測。 我們將單根鑽石奈米線製作成金氧半場效電晶體(MOSFET)，以兩點式探針量測奈米線電阻，量測得到的電阻為21.27M，而以四點式探針量測奈米線電阻為18.89M。對元件施加閘極沒有觀察到通道的變化，有可能是載子濃度低或是介電層的選擇不當造成。接著我們藉由變溫量測及變程跳躍傳輸理論可以推得溫度在295K-81K區間電子有兩種傳輸模式分別為熱活化傳輸及三維變程跳躍傳輸，傳導的自由電子主要來自螢光奈米鑽石表面的sp2碳。

Abstract Diamond nanowire self-assemblies were synthesized from diamond nanoparticles via wet chemical processes in buffered solution at room temperature with different pH values. Nanowire self-assemblies with diameters range from 300 nm to 1200 nm and lengths from 2 m to 10 m were produced. A single diamond nanowire device was fabricated using lithography techniques to study the electrical transport properties in those self-assembled nanowires. The transport properties and temperature dependence in electrical conductivity in temperatures ranging from 300 K to 80 K of single diamond nanowires were reported. I-V characteristics showed linear and symmetrical behavior through the entire temperature range, which indicated that the contacts are ohmic. The resistivity and contact resistance were accurately determined using two- and four-point probe schemes. The transport properties were dominated by the thermal activation of electrons from the Fermi level to the conduction band for a temperature above 220 K and to the three-dimensional Mott variation range hopping at a lower temperature. The conduction electrons are originated from the sp2 carbon on the fluorescent nanodiamonds surface. In the trans-conductance measurements, we find that the electrical conductivity of ND-Cysteamine nanowire can not be modulated by the applied gate bias. This is partially due to poor carrier concentration in the material. Another possible reason is that the appropriate dielectric material should be used in the three-terminal device.