This paper examines whether the Schottky formula ϕss = ET - W is fulfilled during barrier formation for a CdTe(p) crystal. The parameters ϕss, the surface position of the Fermi level, ET, the photoemission threshold and W, the work function, and their changes were determined during oxygen adsorption and In deposition on a CdTe(110) surface freshly cleaved in UHV. The following techniques were used: yield and internal photoemission spectroscopy (YPS, IPS) and contact potential difference (CPD). During oxidation of the CdTe crystal crystal surface ϕss did not change and was equal to 0.52 eV. The first stage of In deposition leads to an ET change of about 80 meV and ϕss changes to 0.98 eV in good agreement with 0.96 eV determined by IPS for the formed diode. The Schottky formula is well fulfilled with a small deviation which corresponds well to the change in ET (80 meV) obtained after the first stages of In deposition and can be correlated to the reactivity of the In with the crystal surface. The long decay time of the surface potential after illumination disappears after the first stages of metal deposition.