monolayer was consistent with the observed difference in the x ray scattering the pentacene on the phenyl silane had a mobility of 0 006 cm 2 v u2212 1 sec u2212 1 while those of the samples that had typical scattering patterns for pentacene all had mobilities greater than 0 1cm 2 v u2212 1 sec u2212 1 the geometry of the phenyl silane appears to have a disruptive influence on the ordering of depositing pentacene as verified by both the x ray and electrical measurements the performance of pentacene layers is also affected by the size of the pentacene crystals u2014 with larger crystals and so fewer grain boundaries having improved electrical performance atomic force microscopy afm was used in the tapping mode to determine the crystal structure of pentacene films deposited on various monolayers the afm images are reproduced in fig7 pentacene deposited on a favorable surface u2014 one that has the terminal ring bond parallel to the surface as depicted in fig1 and 5 u2014 will form large angular terraced crystal structures such as those observed for the cyclopentanetrichlorosilane fig7 a cyclotetramethylenedichlorosilane fig7 b and 1 1 diethoxy 1 silacyclopent 3 ene fig7 c these films also had the highest mobilities in both the linear and saturation regimes the mobilities in the linear regime were 0 35 0 35 and 0 39 cm 2 v u2212 1 sec.