Bias-dependent STM investigations of trimethylgallium adsorption on Si(001) at elevated temperatures

We have studied the change in surface reconstruction of Si(001) after adsorption of 1 L trimethylagllium, Ga(CH3)3 (TMGa) on Si(001). The investigations were carried out by elevated temperature scanning tunneling microscopy (STM) and electron diffraction (LEED, RHEED). Dosing TMGa at a substrate temperature of 500°C leads to a c(4 × 4) surface reconstruction which develops preferentially at trench defects and step edges. These isolated patches grow over time and eventually cover the entire surface. Bias dependent imaging shows that electronic effects dominate the contrast in the STM empty states images. Electron diffraction (LEED, RHEED) confirmed the c(4 × 4) surface reconstruction. Based on our STM images and the results of the electron diffraction experiments, we propose a structural model for the Si(001) c(4 × 4) reconstructed surface after adsorption of TMGa.