本實驗主要藉由一系列變溫的(1)直流電性量測來觀察碳六十多晶薄膜及其上層之金薄膜的電導率,以及(2)在交流變頻電性量測下來探討碳六十多晶薄膜電導率及介電常數;並著重在自旋有序/無序之相變點前後的變化。首先,在直流電性量測下,三明治樣品之碳六十多晶薄膜自旋有序/無序的相變溫度大約在255 K左右,電導率有不連續的現象發生。由2個樣品之量測結果得知相變前後之電導率的變化量,有一樣品約107,另一約2倍。其次,在交流電變頻電性量測下該類樣品之介電常數與電導率會隨溫度變化,由3個樣品之量測結果出現二種不同結果,其中有一樣品在275K (與碳六十分子的相變溫度255K相比,提高了約20K)及另外有兩個樣品在255K之電導率量測皆有不連續的現象。另外,經由對碳六十多晶薄膜上層之金薄膜覆蓋層做變溫的直流電性量測,觀察到在室溫下之金薄膜覆蓋層的電導率與塊材金比較大約下降30倍。由7個樣品之量測結果中,該金薄膜之電導率在255 K附近皆會產生一不連續的現象,並可歸納出三種類型(即相變前後之電導率的變化量,有2個約106,還有2個約102,另3個約2倍,且有類似半導體的特性發生)。最後,實驗結果交叉比對之下,可以顯示金薄膜覆蓋層的電導率之變化與下層之碳六十多晶薄膜的相轉變結構有關連。
This work studies the temperature dependence of (1) DC and AC conductivity σ(T) and dielectric constant ε(T) of the sandwiched C60 polycrystalline films and (2) of the Au-overlayer on top of that films; with emphasis on the changes near the rotational order/disorder phase transition temperature Tc of 255 K. At first, from DC σ(T) for two sandwiched C60 polycrystalline films, the variations of σ(T>Tc)/ σ(T<Tc) are around 107 and 2, correspondingly. Then, from AC σ(T) and ε(T), two different behaviors are found, i.e., Tc = 275 K for one sample, and Tc = 255 K for the other two samples. Furthermore, from DC σ(T) the value of σ(T = 300 K) for the Au-overlayer on top of the polycrystalline film is observed to be a factor of 30 less than that for the Au-crystal;a discontinuity for σ(T = Tc) in all seven samples are surprisingly observed with three types of changes( the variations of σ(T>Tc)/ σ(T<Tc) are categorized as : 106, 102, and 1.4). Finally, above experimental data suggest that the DC σ(T) for the Au-overlayer is closely related to the structural phase transition of the underneath C60 polycrystalline films.