Structural depinning of Ne monolayers on Pb at T < 6/5 K.
We have studied the nanofriction of Ne monolayers with a quartz-crystal microbalance technique at temperatures below 6.5 K and in ultrahigh-vacuum conditions. Very homogeneous and smooth lead electrodes have been physically deposited on a quartz blank at 150 K and then annealed at room temperatures. With such a Pb-plated quartz-crystal microbalance, we have observed a pronounced depinning transition separating a low-coverage region, where the film is nearly locked to the oscillating electrode, from a high-coverage region characterized by slippage at the solid-fluid boundary. Such a behavior has been found to be very reproducible. These data are suggestive of a structural depinning of the solid Ne film when it becomes incommensurate with the lead substrate, in agreement with the results of an extensive molecular-dynamics study.
Bruschi
L
L
Dipartimento di Fisica G. Galilei, Università di Padova, via Marzolo 8, 35131 Padova, Italy.
Fois
G
G
Pontarollo
A
A
Mistura
G
G
Torre
B
B
Buatier de Mongeot
F
F
Boragno
C
C
Buzio
R
R
Valbusa
U
U