Controlled growth of the aromatic p-phenylene oligomer molecules (p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl) adsorbed onto individual KBr(001), KCl(001), NaCl(001), and NaF(001) substrates has been investigated by X-ray diffraction (XRD). XRD analysis provides evidence that the temperature of the alkali halide substrate during deposition, substrate lattice constant, and molecular length affect the molecular orientations within these adsorbed ultrathin films. From this work, oriented films of the above-mentioned p-phenylene oligomer molecules can therefore be grown with varying molecular orientations by careful selection of all appropriate combination of the above deposition parameters. (c) 2005 Elsevier B.V. All rights reserved.