title: Method for measurement of the density of thin films of small organic molecules.
abstract: An accurate and sensitive method is reported to measure the thin-film density of vacuum-deposited, small-molecular organic semiconductor materials. A spectrophotometer and surface profiler had been used to determine the mass and thickness of organic thin film, respectively. The calculated density of tris-(8-hydroxyquinolato) aluminum (Alq(3)) thin film was 1.31+/-0.01 gcm(3). Vacuum pressures and thin-film growth rates are found to have less impact on the thin-film density of organic material. However, the thin-film density of organic material strongly depends on its chemical structure and molecular weight. Specifically, the chemical structure determines the density of organic material that affects the molecular volume and intermolecular stacking.
authors.affiliation: Department of Electrical & Electronic Engineering, Department of Chemistry and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
authors.forename: Hai-Feng
authors.initials: HF
authors.lastname: Xiang
authors.forename: Zong-Xiang
authors.initials: ZX
authors.lastname: Xu
authors.forename: V A L
authors.initials: VA
authors.lastname: Roy
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
authors.forename: P T
authors.initials: PT
authors.lastname: Lai
mesh_terms: D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry*; D012666:Semiconductors; D013053:Spectrophotometry / Q000295:instrumentation*; D013499:Surface Properties; D014618:Vacuum
chemical_list: D009930:Organic Chemicals