We have performed charge transfer phase formation studies on the donor/acceptor system bis(ethylendithio)tetrathiafulvalene (BEDT-TTF)/tetracyanoquinodimethane,(TCNQ) by means of physical vapor deposition. We prepared donor/acceptor bilayer structures on glass and Si(100)/SiO(2) substrates held at room temperature and analyzed the layer structures by optical microscopy, X-ray diffraction and focused ion beam cross sectioning before and after annealing. We found clear evidence for the formation of a charge transfer phase during the annealing procedure. For the as-grown samples we could not detect the occurrence of a charge transfer phase. X-ray diffraction indicated that the monoclinic variant of the (BEDT-TTF)-TCNQ was formed. This was further corroborated by single-source evaporation experiments from pre-reacted (BEDT-TTF)-TCNQ obtained from solution growth, and in particular from co-evaporation experiments of (BEDT-TFF)-TCNQ and TCNQ. In the course of these experiments we found that (0(sic))-oriented BEDT-TTF layers can be prepared on alpha-Al(2)O(3) (11 (2) over bar0) substrates at about 100 degrees C using (BEDT-TTF)-TCNQ as source material. We speculate that due to its high vapor pressure the TCNQ component serves as a carrier gas for BEDT-TTF vapor phase transport. (C) 2009 Elsevier B.V. All rights reserved.