LEEM study of high-temperature oxygen structures on W(110) and their transformations

High-temperature oxygen monolayer structures on W(110) revisited

“…Two dimensional (2D) oxides on W(110) have been a subject of interest since the 1960s [1,2]. This simple system of a single oxygen monolayer chemisorbed on the tungsten surface and ordered at high temperatures has been investigated extensively for many years [3][4][5][6][7][8][9][10][11][12][13][14] as a special case of oxygen adsorption on metal surfaces. In parallel, oxygen adsorbed on W(110) with different sub-monolayer and monolayer coverages posed a model system for investigation of various aspects of adsorptionrelated phenomena, such as surface diffusion [15][16][17][18][19][20][21], kinetics of ordering 2D systems [22][23][24], interactions between adsorbed particles [25,26], surface phase transitions [27][28][29][30][31][32], structure of adsorption phases, [1,3,4,33], adsorption geometry [4,34], electronic [5,7,24,35] and vibrational [36,37] properties, surface stress…”

“…At elevated temperatures (above approximately 500 o C), the stress of the (1x1) monolayer is reduced more effectively via the reorganization of oxygen atoms with slight desorption [4]. This process results in a characteristic spot superstructure in the LEED patterns [1][2][3]9,[12][13][14], whereas the STM measurements show an array of highly ordered, several nanometer-wide stripes 1 with a local structure very close to (1x1) [4,12]. Additionally, the oxygen overlayer annealed above 1000 o C under ultrahigh vacuum (UHV) conditions reveals there are uncovered tungsten rows between the stripes [4].…”

“…Rotational domains also appear as the stripes are aligned at an angle with respect to the high symmetry directions of the substrate. These domains usually span micrometer-sized areas with stripe directions and domain boundaries driven by the substrate step geometry [14]. Depending on the exact oxygen coverage, which is balanced around 1 ML, the oxygen overlayer can be organized in one of the two possible superstructures, which differ as the direction and width of the stripes [1,3,14].…”

“…These domains usually span micrometer-sized areas with stripe directions and domain boundaries driven by the substrate step geometry [14]. Depending on the exact oxygen coverage, which is balanced around 1 ML, the oxygen overlayer can be organized in one of the two possible superstructures, which differ as the direction and width of the stripes [1,3,14]. For the phase that is slightly more oxygen rich, denoted here as the 337-phase, 25-Å wide stripes run along the [33 ̅ 7] or [3 ̅ 37] directions [12,14].…”

“…Depending on the exact oxygen coverage, which is balanced around 1 ML, the oxygen overlayer can be organized in one of the two possible superstructures, which differ as the direction and width of the stripes [1,3,14]. For the phase that is slightly more oxygen rich, denoted here as the 337-phase, 25-Å wide stripes run along the [33 ̅ 7] or [3 ̅ 37] directions [12,14]. Whereas in the case of the 113-phase, with a lower oxygen coverage, the stripes are oriented along the [11 ̅ 3] and [1 ̅ 13] directions [4] and are approximately 30-Å wide [14].…”