Depinning transitions between adsorbate chains coupled by Friedel oscillations

Abstract

The low coverage phase transitions of the p(8ϫ1) and the p(5ϫ1) chain structures of the Sr/Mo͑112͒ system have been investigated with low-energy electron diffraction ͑LEED͒ at constant coverages. It turns out that both structures show similar physics. They first undergo depinning phase transitions at temperatures just below 100 K into striped domain wall structures. The domain wall lattice shows continuous melting at temperatures between 197 and 218 K. Coupling between the adsorbate chains can be described by the potential created by adsorbate-induced charge density waves involving surface states. Within this model domain wall formation appears as thermal excitation of stacking faults on a discrete lattice. For the p(5ϫ1) structure, domain wall formation energies of approximately 65 and 38 meV have been derived for heavy and light walls, respectively, from a fit to the experimental data of depinning.

Structural modifications of quasi-one-dimensional submonolayers by impurity doping

“…For the pure Sr layer, two small anomalies were observed in the integral intensities as a function of temperature, as described in detail in Ref. 16 for the pure system. The anomaly close to 96 K was attributed to a depinning transition of the Sr chain lattice, since it was found to be correlated with the onset of a change of the average lattice constant, 16 whereas the anomaly at 197 K marks melting of the chain lattice, indicated by a significant acceleration of the loss of long range correlations mainly in the ͓110͔ direction.…”

“…8,16,18,19 The base pressure in the vacuum chamber between 0.7 and 1.5 ϫ 10 −11 mbar was kept all the time, i.e., both during deposition and subsequent measurements.…”

“…16 In order to test the proposed coupling mechanism between chains-a mixture of dipole-dipole repulsion and an oscillatory part due to the charge density waves 10 -but also to demonstrate its limitations, we added electronegative atomic oxygen to the ordered structures of electropositive Sr at low coverages. We show that, contrary to the generally accepted role of impurities to destroy long range order, oxygen is able to even stabilize and modify long range order at concentrations far below one atom per unit cell.…”

Monte Carlo study of linear chain submonolayer structures. Application to Li/W(112)

“…This fact has not been observed experimentally in Li/W(1 1 2), maybe due to narrow temperature range of stability of IC phase. On the other hand, the commensurate--incommensurate transition has been recently found in Sr/Mo(1 1 2) [13]. Therefore, it would be very interesting to determine experimentally the whole (T ; H) phase diagram of Li/ W(1 1 2) to check theoretical prediction.…”

Fermi surface of Mo(112) and indirect interaction between adsorbed atoms

“…The surface of the Mo(112) sample was cleaned by the standard method of repeated annealing (at ~1400° C) in oxygen atmosphere with the oxygen partial pressure of ~1×10 -6 torr, followed by cycles of annealing (at 1000-1300° C) and flashing (at ~1800°C) similar to the procedures used elsewhere [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][32][33][34][35][36][37][38]40,43,45,[51][52][53]62]. Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to verify the quality of the Mo(112) surface, including the periodic structural order.…”