Structure and Defects in Thin C60 Films

Thin C₆₀ films were deposited by vacuum sublimation of soot on single-crystal and amorphous substrates. The absence of higher fullerenes was confirmed by IR, Raman and UV-VIS spectroscopy. X-ray diffraction revealed a high density of stacking faults (probabilities in the range 10^-2), correlated with lattice distortions. Analysis of the UV-VIS absorption bands yielded values of the h_u → t_1g and h_u → t_1u optical gaps.     

Optical Transition in Reduced C60 Thin Films

Absorption spectra of C60 thin film reduced in an electrochemical cell are studied. The results are compared with data of chemically reduced C60 anions. Absorption with relatively broad line-width below the energy of 1 eV is observed in the film besides the peaks at 1.14 ∼ 1.4 eV observed in C60 anion solution. The electronic states of reduced COT are discussed in terms of the solid state effect.     

Electronic Properties of C60 Thin Films

Abstract

The electronic structure of polycrystalline C₆₀ thin films has been investigated using surface photovoltage spectroscopy (SPS) and conductivity measurements. the films show n-type semiconductivity with an activation energy of ～ 0.8 eV as found from the temperature dependence of the conductivity at high temperatures. the electronic structure emerging from our SPS results comprises a 1.6 eV photo-conduction gap, a mobility gap of about 2.25 eV and two gap states, a donor and an acceptor, at 0.35 eV and (1.0-1.1) eV, respectively, below the photo-conduction edge. the results indicate the possibility of the existence of band tails, extending into the optical gap of these films, as well as other deep gap states.     

Electronic Properties of C60 Thin Films

The electronic structure of polycrystalline C₆₀ thin films has been investigated using surface photovoltage spectroscopy (SPS) and conductivity measurements. the films show n-type semiconductivity with an activation energy of ∼ 0.8 eV as found from the temperature dependence of the conductivity at high temperatures. the electronic structure emerging from our SPS results comprises a 1.6 eV photo-conduction gap, a mobility gap of about 2.25 eV and two gap states, a donor and an acceptor, at 0.35 eV and (1.0-1.1) eV, respectively, below the photo-conduction edge. the results indicate the possibility of the existence of band tails, extending into the optical gap of these films, as well as other deep gap states.     

The Electroforming Effect in Polycrystalline Fullerene C60 Films

Technical Physics Letters - Long-term exposure of a polycrystalline fullerene C60 film in a constant electric field of 1–4 MV/cm produces an electroforming effect manifested by increase in...     

Nonlinear Optical Characteristics of C60 Thin Films

Abstract

The results of investigation of the real and imaginary parts of third‐order nonlinear susceptibility (χ⁽³⁾) of C₆₀ thin films (～100 nm) at the wavelength of Nd: YAG laser radiation (532 nm, τ = 55 ps) are presented using Z‐scan technique. Our studies show that the sign of Reχ⁽³⁾ changes from negative, at pulse repetition rate of 2 Hz to positive, at 0.5 Hz. Sign variations of the real part of the third‐order susceptibility were attributed to the influence of the thermal lens.     

Preparation of C60 Thin Films and Cs-Rb Doping

The effect of preparation conditions onto the crystallinity of C₆₀ thin films were studied by using two different vapor deposition methods. Rb and Cs were found to be doped in C₆₀ thin films by the resistance measurement during the course of the doping experiment. The Rb/Cs-doped film showed a superconducting transition at Tc(onset)=24±3K and Tc(zero)=8K.     

掺锡C60薄膜材料的电子结构与电导性研究

本文报道了锡掺杂C6 0 薄膜样品的扫描电镜 ,X射线衍射 ,紫外可见吸收光谱和电阻随温特性的测量结果 ;显示样品由纳米级颗粒组成 ,为面心立方结构 ,掺杂锡原子在禁带中形成施主能级 ,电阻随温度增加呈指数衰减 ,霍耳效应证实为N型半导体。     

C60-PMMA复合膜的纳米结构研究

采用化学有机沉积法,在Ｓｉ（１００）、ＫＢｒ压片及微栅衬底上分别制备了 Ｃ_６０／ＰＭＭＡ重量比不同的Ｃ_６０－ＰＭＭＡ复合膜．红外光谱分析表明,Ｃ_６０分子已均匀地分布在Ｃ_６０－ＰＭＭＡ复合膜中．利用Ｘ射线衍射（ＸＲＤ）谱和透射电子显微镜（ＴＥＭ）研究了该复合膜的结构,结果显示原来均匀分布在ＰＭＭＡ中的Ｃ_６０分子经过扩散趋向于形成非晶或晶化的Ｃ_６０颗粒．经过退火,以面心立方结构单晶形式存在的Ｃ_６０颗粒的尺寸为３０～１００ｎｍ,且以规则的几何形体分散在ＰＭＭＡ连续相中．玻耳兹曼能量分布规律能够较好地解释,提高Ｃ_６０含量或退火温度,晶化Ｃ_６０颗粒尺寸增大的现象．     

Temperature Dependence of Optical Spectra of C60 Thin Films

Abstract

We examine the temperature-induced changes of the optical spectra of thin C₆₀ films deposited on silicon and gold. We have used thermoreflectance to study the spectral response of the lowest electronic states. We have found strong effects related to the phase transition and freezing of the rotations of C₆₀ molecules upon cooling.     

Temperature Dependence of Optical Spectra of C60 Thin Films

We examine the temperature-induced changes of the optical spectra of thin C₆₀ films deposited on silicon and gold. We have used thermoreflectance to study the spectral response of the lowest electronic states. We have found strong effects related to the phase transition and freezing of the rotations of C₆₀ molecules upon cooling.     

Adhesion and Strength Properties of C60 Films on Silicon Substrates

Abstract

Direct pull tests were used to examine the adhesion and rupture strength of C₆₀ films on a silicon substrate. The measured strength values were in the range of 3.5-15 MPa depending on deposition conditions. The cohesive fracture inside the fullerite film due to strong bonding at the film/substrate interface was predominantly observed. Comparison of the rupture strength and microhardness is made. The results show that adherence of C₆₀ film to a silicon substrate is high enough for various technological applications.     

Effects of Annealing on the Conductivity of C60 Thin Films

Films of C₆₀, at different stages of annealing of T_t=200°and 300°C have been electrically characterized over the temperature domain from -130°C to T_t. X-ray diffraction revealed a random polycrystalline fee structure with stacking defects of an intrinsic nature, due to deposition conditions. The value of room-temperature conductivity was found to be in the range (6.3-1.0) *10^-10 (0cm)^-1. In the stable annealed state the conductivity showed an activated temperature dependence above 423 K and a non-activated dependence below 330-280 K. The activation energies E_a = 0.8 eV (film thickness 0.70 μm) and E_a = 1.0 eV (film thickness 2.40 μm) were in good agreement with the energy gap values (1.63 eV and 2.08 eV) which were deduced from the absorption spectral dependence. Annealing decreased the non-activated contribution to conduction, extending the intrinsic conduction temperature range.     

Adhesion and Strength Properties of C60 Films on Silicon Substrates

Direct pull tests were used to examine the adhesion and rupture strength of C₆₀ films on a silicon substrate. The measured strength values were in the range of 3.5-15 MPa depending on deposition conditions. The cohesive fracture inside the fullerite film due to strong bonding at the film/substrate interface was predominantly observed. Comparison of the rupture strength and microhardness is made. The results show that adherence of C₆₀ film to a silicon substrate is high enough for various technological applications.     

Structure of C60 Thin Films Formed by Ionized Cluster Beam Deposition

C₆₀ thin films were formed on cleaved NaC1 substrates at room temperature and their crystallinity and crystal orientation were found to be controlled by acceleration and ionization voltages of ionized cluster beam (ICB) technique.     

氩气氛下制备的C60薄膜的形貌、结构和光学性质

用原子力显微镜(AFM)、X射线衍射(XRD)、红外光谱(IR)及紫外-可见光谱(UV/VIS)研究了在氩(Ar)气氛下制备的C60薄膜的表面形貌、结构及光吸收特性.发现其UV/VIS的强度和吸收峰位置明显不同于在真空中制备的G60薄膜.与真空中制备的C60薄膜比较,所研究薄膜的红外谱没有变化,但X射线衍射表明其结构从面心立方(fcc)相变成fcc相与六角密堆(hcp)相的混合相.AFM表明,在Ar气氛中制备的C60薄膜有较大的表面粒子,并且表面生长岛更尖锐.这将有利于G60薄膜的场电子发射.