Gadolinium-doped, yttrium oxide thin films have been deposited on silicon (001) substrates by radio-frequency (RF) magnetron reactive sputtering that exhibit cathodoluminescence (CL) at ultraviolet frequencies. The maximum CL brightness occurred at lambda-314-315 nm characteristic of the P-6(3/2) -> S-8 (lambda = 3 14 nm) transition observed in Gd-doped, yttrium oxide powders. The radiative recombination takes place at the rare earth activator Gd3+ site embedded in the Y2O3-delta host; the optical transition resides within the band gap of the Y2O3-delta host and the transition observed is characteristic of atomic gadolinium. A combinatorial approach to sputtering was used to deposit a film of variable composition from 1 to 23 at.% Gd in Y2O3-delta in order to rapidly discern the composition node of optimal CL brightness. A simulation was created for the purpose of predicting the film combinatorial composition for binary and ternary alloys prior to sputtering experiments in order to facilitate our combinatorial thin film synthesis technique. The model prediction varied from the real experimental composition profile by only 2.2 at.% Gd +/- 1.6 at.% proving the predictor as a useful aide to complement combinatorial thin film experiments. A film of composition Y1.56Gd0.44O3.25 (8.3 at.% Gd) yielded the maximum CL brightness. CL brightness increased continuously up to the 8.3 at.% Gd composition due to the increased number of activators present in the host. Beyond this composition the brightness drastically decreased. The oxygen composition in the combinatorial film was strongly dependent on the Gd composition; films were sub-stoichiometric delta > 0 below similar to 6 at.% Gd and was over-stoichiometric delta < 0 beyond this composition. (c) 2006 Elsevier B.V All rights reserved.