The environmental impact resulting from the use of fossil fuel as an energy source affects the entire globe. Eventually, fossil fuels will no longer be a reasonable source of energy and alternative energy sources will be needed. Thermoelectric materials (TE) that directly convert heat into electricity are a viable option to replace the conventional fossil fuel because they are reliable, cost effective, and use no moving parts. Recently researchers discovered the existence of giant Seebeck coefficient in manganese oxide (MnO2) powders, which ignited an increased interest in MnO2-based materials. In this work we present a systematic structural and electrical characterization of amorphous and crystalline MnxOy thin films. These films were deposited at room temperature on heated silicon and sapphire substrates by DC Magnetron Sputtering. Our preliminary results show that MnxOy/silicon thin films undergo a crystalline change from Mn2O3 to Mn3O4 as annealing temperature is increased from 300°C to 500°C.