We consider the lattice version of the free field in two dimensions (also called harmonic crystal). The main aim of the paper is to discuss quantitatively the entropic repulsion of the random surface in the presence of a hard wall. The basic ingredient of the proof is the analysis of the maximum of the field which requires a multiscale analysis reducing the problem essentially to a problem on a field with a tree structure.
"Entropic Repulsion and the Maximum of the two-dimensional harmonic." Ann. Probab. 29 (4) 1670 - 1692, October 2001. https://doi.org/10.1214/aop/1015345767