The surface of indium tin oxide (ITO) in organic light emitting diodes (OLEDs) was treated using an atomic layer deposition with tetrakis(ethylmethylamino) hafnium (TEMAH) and O2 precursors. The treatment for 5 cycles at room temperature resulted in a significant improvement in the electroluminescent characteristics resulting from the increased hole injection. According to the various characterizations, an ultra-thin HfOx layer without any insulating properties was formed, which modified the electronic band structure of the ITO anode. When the number of cycles or temperature was increased, an electrically insulating HfOx was formed, and the resulting OLED properties deteriorated.