Observation of Molecular Layers in (2-(4,5-bis(thiomethyl)-1,3-dithiol-2-ylidene)-5- (4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene) (TMET-TTP) Single Crystals by Means of Scanning Tunneling Microscopy