The elastic mean free path of carriers in a recently introduced model
of quantum chaotic billiards in two and three dimensions is calculated
The model incorporates surface roughness at a microscopic scale by ra
ndomly choosing the atomic levels at the surface sites between -W/2 an
d W/2. Surface roughness yields a mean free path l that decreases as L
/W-2 as W increases, L being the linear system size. But this diminuti
on ceases when the surface layer begins to decouple from the bulk for
large enough values of W, leaving more or less unperturbed states on t
he bulk. Consequently, the mean free path shows a minimum of about L/2
for W of the order of the bandwidth. Energy fluctuations reflect the
behavior of the mean free path. At small energy scales, strong level c
orrelations manifest themselves by small values of Sigma(2)(E) that ar
e close to random matrix theory (RMT) in all cases. At larger energy s
cales, fluctuations are below the logarithmic behavior of RMT for l>L,
and above RMT value when l<L.