Calorimetric study of the desorption and phases of 3He and 4He adsorbed on two layers of H2-plated graphite above 0.2K

We have conducted new heat capacity studies of films of He-3 and He-4 adsorbed on 2.15 layers of hydrogen plating exfoliated graphite for temperatures T > 0.2K and coverages (n) over the entire first layer and beginning of the second layer. Low-density He-3 films show two-dimensional Fermi fluid behavior with no liquid-vapor condensation below 0.9K. We have mapped the n-T melting line and estimated monolayer completion density using heat capacity isotherms. By fitting He-3 films' desorption specific heats to a theoretical model, we have calculated the He-3 binding energy (21.3K to 21.7K) and compare it to a previous measurement for He-4 films on the same substrate (25.1K to 25.5K).