Prewetting of liquid hydrogen on rough cesium substrates

Area of Science:

• Surface Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Prewetting phenomena are crucial for understanding thin film formation.
• Substrate roughness and defects significantly influence film morphology and dynamics.
• Van der Waals forces govern the interactions in physisorbed systems.

Purpose of the Study:

• To investigate the prewetting dynamics of hydrogen (H2) on rough cesium (Cs) substrates.
• To analyze the impact of substrate defects on the thin-film boundary.
• To compare prewetting and wetting dynamics and their underlying models.

Main Methods:

• Low-temperature deposition of Cs substrates.
• In-situ observation of H2 prewetting dynamics.
• Analysis of the thin-film boundary geometry and pinning effects.

Main Results:

• The boundary between thin and thick van der Waals films of H2 is strongly pinned by Cs substrate defects.
• Substrate defects cause significant distortion of the prewetting film morphology.
• The dynamics and geometry of the thin-thick boundary deviate from predictions of simple 1D models.

Conclusions:

• The behavior of the thin-thick boundary is complex and cannot be described by simplified models.
• The finite width of the boundary leads to dynamics resembling those of a contact line.
• Understanding these dynamics is essential for controlling thin film growth on imperfect surfaces.