Scanning probe microscopy offers the possibility of probing physical properties with high spatial(resolution).In particular

scanning tunneling microscopy(STM) and scanning tunneling spectroscopy(STS) can be used to combine structural characterization with probing the electronic signature of the organic compounds on a molecular scale.A number of STS investigations on organic materials have been published in(recent) years.And most of the authors observed electron transport through the frontier orbitals of the organic molecules(

i.e

.

through the highest occupied molecular orbital(HOMO) and the lowest unoccupied mole-(cular) orbital(LUMO).The measurements of the contributions of the second filled and second unfilled molecular orbitals to the tunneling current have also been studied in a few researches.Compared with other methods of molecular energy structure characterization

such as Ultraviolet-Visible Spectrophotometry(UV-Vis)

(Cyclic) Voltammetry(CV) and Ultraviolet Photoelectron Spectroscopy(UPS)

STM/STS can show the nano-sized surface microscopy of the molecule in real time and the detailed information of surface roughness and graininess of the thin solid film can be obtained.The STM/STS measurement has become a powerful tool for the study of nanostructures in numerous areas of science and technology.The application of STM/STS in the field of(organic) light-emitting diodes(OLEDs) is promising.We present here a study of vapor deposition thin film(layers) of tris(8-hydroxyquinolino) aluminum(Alq

3

)

4-(2-(3

3-dicyano-methylene-5

5-dimethyl-1-(cyclo)-hexylidene)vinyl)phenyl(1-naphthyl)phenyl-amine(DPN-2CN)

and 4-(2-(3

3-dicyano-methylene-5

5-dimethyl-1-cyclohexyl-idene)vinyl)phenyldi(1-naphthyl)-amine(DNP2CN) on the substrate of ITO.The surface electronic structures of organic light-emitting materials Alq

3

DPN-2CN and DNP-2CN were studied by STM/STS.The obtained E

LUMO

of compound DPN-2CN were 3.50 eV and 3.51 eV respectively.And the(energy)-band parameters of DPN-2CN and DNP-2CN were determined by comparing their surface electronic structures with Alq

3

.The energy-band parameters of DPN-2CN and DNP-2CN obtained from the above method was compared with the result of CV experiments.The E

LUMO

obtained from CV experiment is 3.68 eV for compound DPN-2CN

and 3.69 eV for compound DNP-2CN respectively.The result of STM/STS was basically in accordance with that of CV.