Two-domains bulklike Fermi surface of Ag films deposited onto Si(111)-(7x7)

Thick metallic silver films have been deposited onto Si(111)-(7x7) substrates at room temperature. Their electronic properties have been studied by using angle resolved photoelectron spectroscopy (ARPES). In addition to the electronic band dispersion along the high-symmetry directions, the Fermi surface topology of the grown films has been investigated. Using ARPES, the spectral weight distribution at the Fermi level throughout large portions of the reciprocal space has been determined at particular perpendicular electron-momentum values. Systematically, the contours of the Fermi surface of these films reflected a sixfold symmetry instead of the threefold symmetry of Ag single crystal. This loss of symmetry has been attributed to the fact that these films appear to be composed by two sets of domains rotated 60$^o$ from each other. Extra, photoemission features at the Fermi level were also detected, which have been attributed to the presence of surface states and \textit{sp}-quantum states. The dimensionality of the Fermi surface of these films has been analyzed studying the dependence of the Fermi surface contours with the incident photon energy. The behavior of these contours measured at particular points along the Ag $\Gamma$L high-symmetry direction puts forward the three-dimensional character of the electronic structure of the films investigated.Comment: 10 pages, 12 figures, submitted to Physical Review

Photoemission and scanning tunneling microscopy investigation of elemental-semiconductor surfaces

The clean and reacted surfaces of Si(111)-(7x7), Si(100)-(2x1), Ge(111)-c(2x8), and Ge(100)-(2x1) have been studied to better understand the nature of these elemental-semiconductor surfaces. By carefully monitoring the adsorbate-induced changes in the electronic properties at the surface via spectroscopic methods such as photoemission, and by studying the resulting surface structures by scanning tunneling microscopy (STM), a quantitative description of the interaction and reaction between adsorbate and surface can be obtained. The photoemission method allows a distinction between atoms in different layers and in inequivalent sites by their binding energy shifts. By comparison with structural models and reference samples the number of atoms in each distinct chemical configuration can be determined. An adsorbate-induced chemical shift can be correlated with electronegativity differences between substrate and adsorbate atoms. In particular, studies of noble-metal interfaces with the (100) faces of Si and Ge demonstrate this novel combined application of photoemission and STM.The (111) faces of Si and Ge reconstruct to exhibit rather complex chemisorption geometries which are generally not well understood. For clean Si(111)-(7x7), there are three distinct surface sites giving rise to three different chemical environments. To establish the correlation between various surface-shifted components of the core levels and the surface sites, several experiments were designed and performed. The main idea behind these experiments has been to selectively replace atoms or saturate the dangling bonds of a certain surface site by adsorbate atoms, using the noble metal-semiconductor interface as the model system to test this basic approach. Results for other interface systems such as Sb, Sn and NH\sb3 with these semiconductors are also presented for comparison. These studies indicate that the "adatoms" on the clean Si(111)-(7x7) surface are directly responsible for the metallic surface state in the valence band. Additionally these adatoms exhibit a core level shift of $-$0.77 eV relative to the bulk atoms.U of I OnlyETDs are only available to UIUC Users without author permissio

Treatment of Chronic Venous Ulcer with Cold Atmospheric Plasma Jet

Nowadays, cold atmospheric plasma jet (CAP-jet) shows interesting results in the dermatology sector, particularly focusing on wound healing and antimicrobial properties. The purpose of this case report is to present a nonthermal atmospheric pressure plasma treatment as a novel therapy for venous ulcers. The plasma consists of ionized helium gas that is produced by a high-voltage (4.5 kV) and high-frequency power supply (22 kHz). We here present a 65-year-old man with a slow-healing ulcer on the right lower limb. The CAP was applied to the ulcer twice a week for four consecutive weeks and the patient was followed for 6 weeks. The amount of exudate, ulcer size, and wound grading were determined weekly. The results showed that exudate from the ulcer significantly reduced in the first week after complete treatment, the wound grading of the ulcer improved by the second week, and the size of the ulcer significantly decreased after 2 weeks. The ulcer entirely healed after 4 weeks without any signs of infection. This case study demonstrates that applying CAP-jet can decrease the bacterial load on the ulcer site and stimulate tissue regeneration concurrently. This increases the speed of the healing process

Selective area, synchrotron radiation induced, delta doping of silicon

We have used broadband synchrotron radiation to induce selective area surface doping of boron into silicon. The source of the boron was nido-decaborane (B10H14) adsorbed on Si(111) at 100 K. Irradiation caused decomposition of the adsorbed molecule which lead to an enhanced concentration of free boron in the irradiated area. Using Si 2p core level photoelectron spectroscopy, the surface chemical composition and Fermi level position in both the irradiated and unirradiated regions were determined. The downward movement of the Fermi level was greater in the irradiated region than in the unirradiated region, and greater for n-type than for p-type Si