The brief steps:
i) build a crystal structure of SiO2 using vnl;
ii) cleave a surface structure (i.e., (001)surface) of SiO2 and export the atomic coordinates into a file, and then convert it into a xyz file;
iii) build a crystal structure of Si and then take it as electrodes to build a two probe system. In this two-probe system, the distance between center region and the right electrode is set as large enough (i.e, above 10 Angstrom). Export it as an equivalent bulk system and save its script file.
iv) Edit the script file, remove the coordinates of atoms in the right electrode. So the interface is consisted of the left electrode and the center region, and the vacuum thickness equals to the distance defined in the step iii) plus the length of the right electrode.
