Barnes Teresa M, Blackburn Jeffrey L, van de Lagemaat Jao, Coutts Timothy J, Heben Michael J
National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
ACS Nano. 2008 Sep 23;2(9):1968-76. doi: 10.1021/nn800194u.
We present a comprehensive study of the effects of doping and temperature on the conductivity of single-walled carbon nanotube (SWNT) networks. We investigated nearly type-pure networks as well as networks comprising precisely tuned mixtures of metallic and semiconducting tubes. Networks were studied in their as-produced state and after treatments with nitric acid, thionyl chloride, and hydrazine to explore the effects of both intentional and adventitious doping. For intentionally and adventitiously doped networks, the sheet resistance (R(s)) exhibits an irreversible increase with temperature above approximately 350 K. Dopant desorption is shown to be the main cause of this increase and the observed hysteresis in the temperature-dependent resistivity. Both thermal and chemical dedoping produced networks free of hysteresis. Temperature-programmed desorption data showed that dopants are most strongly bound to the metallic tubes and that networks consisting of metallic tubes exhibit the best thermal stability. At temperatures below the dopant desorption threshold, conductivity in the networks is primarily controlled by thermally assisted tunneling through barriers at the intertube or interbundle junctions.
我们对掺杂和温度对单壁碳纳米管（SWNT）网络电导率的影响进行了全面研究。我们研究了近乎纯类型的网络以及由精确调谐的金属管和半导体管混合物组成的网络。对网络在其制备状态以及用硝酸、亚硫酰氯和肼处理后进行了研究，以探索有意掺杂和偶然掺杂的影响。对于有意和偶然掺杂的网络，在温度高于约350 K时，薄层电阻（R(s)）呈现不可逆增加。掺杂剂解吸被证明是这种增加以及所观察到的与温度相关的电阻率滞后现象的主要原因。热去掺杂和化学去掺杂都产生了无滞后的网络。程序升温脱附数据表明，掺杂剂与金属管的结合最强，并且由金属管组成的网络表现出最佳的热稳定性。在低于掺杂剂解吸阈值的温度下，网络中的电导率主要由通过管间或管束间结处的势垒的热辅助隧穿控制。
