Epitaxial growth of long‐chain molecules on potassium hydrogen phthalate and potassium chloride substrates from the vapor phase

Abstract

AbstractPentacontane, hexacontane, 15‐ketohentriacontane (palmitone), and solid solutions of the two n‐paraffins were deposited from the vapor phase onto surfaces of potassium hydrogen phthalate (PHP) crystals and cleavage faces of potassium chloride (KCl) crystals in vacuo. Epitaxial growth, with molecular chains parallel to the substrates, occurs within a temperature range (e.g., 25–50°C for palmitone), and the epitaxial relationship between molecules and substrates was broken at higher temperatures. The electron diffraction patterns, similar to that of polyethylene, were obtained from all samples prepared at room temperature. The [100] or [130] directions of palmitone crystals are parallel to the substrate surface of PHP, and the [110] direction is parallel to that of KCl; the crystals in both cases are the orthorhombic form with lattice parameters a = 7.56 Å, b = 4.93 Å, c = 82.8 Å and a space group of Pna21. The (100) planes of n‐paraffin crystals are parallel to the surface of PHP, and the crystals are again orthorhombic. Also, solid solutions of n‐paraffins can be formed from the vapor phase, with the nucleation process on the two substrates being the same as for pure paraffins.