懸浮二硒化錸場效電晶體電子傳輸之研究

Electrical properties of Suspended ReSe2 Field-Effect Transistor

蘇恬嬅(Tien-Hua Su)

指導教授 ： 簡紋濱

國立交通大學/理學院/理學院應用科技學程/碩士(2018年)

摘要

多數的場效電晶體在製作樣品時，都是將實驗材料直接與介電材料基板做結合，以矽基板舉例，矽基板本身有缺陷，會導致電子侷限在缺陷裡，影響場效電晶體所測量的元件效能，因此在本實驗中，以懸浮的方式製作場效電晶體，確保量測到的數據不受基板雜質因素影響。
本實驗以機械剝離法將二硒化錸從原塊分離為少數層，再將二硒化錸轉印到金電極上，讓二硒化錸只有與金電極直接接觸，其餘懸空於基板上，為了提升電極與材料的接觸，利用電子束微影及熱蒸鍍在電極上方的二硒化錸薄片上加鍍金屬電極，再利用高低溫退火來增加接觸與降低接觸電阻，製作出懸浮二硒化錸薄片之場效電晶體樣品。藉由電性量測系統，將源極與汲極的電壓差固定在1 V，測量溫度範圍在80 K到300 K區間，改變閘極電壓大小，觀察在不同溫度與閘極電壓下，懸浮二硒化錸場效電晶體的阻抗、電導率與載子遷移率的變化。
在溫度為300 K時，懸浮二硒化錸場效電晶體開關電流比為〖10〗^3，閘極電壓與汲極和源極電流曲線呈現n型半導體行為，阻抗隨著溫度上升而下降，呈現負電阻溫度係數的半導體材料特性。其電導率隨溫度變化在80 K到180 K區段，由於雜質游離效應影響，電導率隨溫度下降而變小，其行為能利用Mott二維變程跳躍理論擬合，擬合得到的無序程度參數之特徵溫度(T_0)會隨著閘極電壓增加，即載子濃度提升使得特徵溫度變小。懸浮二硒化錸場效電晶體的載子遷移率在溫度範圍80 K到300 K區間，隨著溫度上升載子遷移率增加，因為當溫度上升，價電子獲得能量躍遷至傳導帶，使得載子遷移率增加，但在200 K 到240 K區間，載子遷移率變化趨勢與其他溫度區域不同。

關鍵字

二硒化錸 ； 懸浮 ； 場效電晶體 ； 電導率 ； 載子遷移率

並列摘要

ReSe2 is one of transition metal dichalcogenides with triclinic layer-type structure. Many researches have demonstrated the application potential of ReSe2 in semiconductor technology. However, it was uncovered that the electrical properties of of supported ReSe2 field-effect transistors (FET) suffer from impurity scattering from the substrate. In this research, we make suspended ReSe2 FETs and explore their electrical properties at different temperatures and under different gating voltages.
The as-fabricated suspended ReSe2 FET devices show an on/off ratio of about 〖10〗^3 at 300 K. The source-drain current-voltage behavior and the transfer characteristics shows an n-type feature for the ReSe2. We further analyzed the temperature-dependent conductivity which decreases with decreasing temperature in the temperature range from 80 to 180 K. The temperature behaviors were well fitted by using Mott’s variable range hopping model. We can estimate the disorder parameter (characteristic temperature) T_0 and we found that the T_0 parameter decreases with increasing gating voltages. In addition, we estimated the mobility from the gating behavior and discovered that the mobility increases with increasing temperature in the range from 80 to 300 K.

並列關鍵字

ReSe2 ； Suspended ； mobility ； conductivity

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