Mesostructured thin films deposited by PECVD from TMGe

The plasma enhanced CVD (PECVD) is proposed as an effective tool for preparation of the mesostructured thin films. The technique is compatible with silicon technology, which makes it interesting from potential applications point of view. Thin layers deposited by this method, using tetramethylgermane (TMGe) as a source compound, can be deposited in forms characterized by various structures in nanometer-scale range. Depending on the process parameters both homogenous distribution of carbon and germanium atoms in the material as well as specific nanostructure with germanium and carbon rich regions can be fabricated. The structure differences have an obvious impact on the electronic properties of the material and result in two kinds of electronic structure—namely amorphous insulator (a-I) and amorphous semiconductor (a-S), respectively. The two-level structure has been observed in the a-S films. The first level consists of germanium grains (few nanometers in size) embedded in the carbon matrix. The grains are no randomly distributed in the material but agglomerate forming domains of about 60 nm in size defining the second level structure.The paper concentrates on the deposition technology which leads to the a-S films and presents results of investigations implying the existence of the mesostructure in this material. Among applied experimental techniques the most interesting results have been achieved by Raman spectroscopy, impedance spectroscopy and charge sensitive scanning probe microscopy (SPM).