The main optical, dark and photoconductivity, photo‐emf, and photoemission characteristics are studied for thin‐layers of pentacene (Pc) crystals. It is shown that in the h = = 2.2 to 4.0 eV spectral region intrinsic photogeneration is dominant in Pc crystals, presumably proceeding via an autoionization mechanisms with a threshold value Ec = = (2.20 ± 0.05) eV. Whereas in the hvv = 1.4 to 2.2 eV spectral region an exciton photogeneration mechanism, namely, generation of excess charge carriers through triplet exciton‐trapped hole interaction, seems most probably. The energy level spectra of neutral and ionized states of the Pc crystal are determined. The Pc crystal ionization energy Ic equals to (5.07 ± 0.05) eV; the forbidden energy gap ΔE0 = (2.20 ± 0.05) eV; the intrinsic dark conductivity activation energy E a0 = ΔE0/2 = (1.15 ± 0.15) eV. The electron affinity Ac of the Pc crystal, determined by three independent methods equals to (2.87 ± 0.10) eV, (2.70 ± 0.15) eV, or (2.73 ± 0.2) eV, respectively. The characteristic energies of the quasi‐continuous trap distribution for vacuum evaporated thin Pc crystals layers are kTc = 0.12 eV in an exponential approximation and ± = 0.28 eV in a Gaussian one as determined from SCLC measurements.

The energy gap and the ionization energy of crystals are estimated using a more precise correlation. An empirical correlation function for different energy levels of polyacene molecules and crystals have been determined. Some conclusions are made.

This paper reviews the different types of merit functions that have been used in the past in optical thin film calculations. Attention is drawn to the power of merit functions which operate on complicated quantities that require one or more integral expressions for their definition. To prove this point, several thin film problems are solved in which the CIE coordinates, luminous transmittances or reflectances, solar absorptance, and blackbody emittances of a multilayer are specified.

Plasma cleaning is common in the preparation of titanium medical devices. In this study, we examine the use of continuous in situ measurements with optical emission spectroscopy (OES) during plasma cleaning and wet contact angle as a tool to assess titanium implant cleanliness. Plasma cleaning was performed in argon plasma at 66.7 Pa in a commercially available radio-frequency (RF) power plasma system using 25 or 100 W of power. During cleaning, the intensities of OES lines at 386 and 418 nm, as related to surface contaminants, decreased over time and reached a baseline level in ~1 h. However, the water contact angle (WCA) decreased more rapidly, reaching ≤10 degrees in 3-5 sec and further decreased to the limit of detection of ~1 ± 1 degree in 20 min using 25 W plasma and in 1 min using 100 W plasma. The OES data indicate that plasma cleaning starts with rapid removal of contaminants from pronounced regions that are better exposed to the plasma and is followed by prolonged cleaning related to the removal of contaminants from less accessible regions. The delayed rise in WCA demonstrates a limitation in using that technique to assess cleanliness and shows how OES is a useful tool to better understand and control plasma cleaning of titanium surfaces.