Surface degeneration of W crystal irradiated with low-energy hydrogen ions

Abstract

The damage layer of a W (100) crystal irradiated with 120 eV hydrogen ions at a fluence of up to 1.5 × 1025/m2 was investigated by scanning electron microscopy and conductive atomic force microscopy (CAFM). The periodic surface degeneration of the W crystal at a surface temperature of 373 K was formed at increasing hydrogen fluence. Observations by CCD camera and CAFM indicate the existence of ultrathin surface layers due to low-energy H irradiation. The W surface layer can contain a high density of nanometer-sized defects, resulting in the thermal instability of W atoms in the surface layer. Our findings suggest that the periodic surface degeneration of the W crystal can be ascribed to the lateral erosion of W surface layers falling off during the low-energy hydrogen irradiation. Our density functional theory calculations confirm the thermal instability of W atoms in the top layer, especially if H atoms are adsorbed on the surface.

Current mapping of low-energy (120 eV) helium and hydrogen irradiated tungsten by conductive atomic force microscopy

“…The size and density of defects are strongly dependent on H fluence, and ordered arrangements of defects are formed at relatively high H energy and irradiation temperature. Our recent study shows that due to low-energy H irradiation at 373 K, the W surface layer contains a high density of nanometer-sized defects, resulting in the thermal instability of W atoms in the surface layer and a periodic surface degeneration of the W lattice [12]. The surface topography of H irradiated W in Fig.…”

Tungsten–Carbon Nanotube Composite Photonic Crystals as Thermally Stable Spectral‐Selective Absorbers and Emitters for Thermophotovoltaics

“…[28,50] In our work, the nanocavities in the W-CNT PhCs are realized by infiltration of the nanopatterned CNT forests with W, rather than top-down etching of a single material. Our approach avoids residual etching contaminates and processinduced surface defects which are known to degrade surface integrity of W. [68][69][70] The geometry of our pattern is intrinsically stable, as the surface diffusion rate over the whole W-CNT PhCs is uniform, and the surface diffusion of W in between individual Al 2 O 3 -coated CNTs is not energetically favorable.…”