3:15 PM - 3:30 PM
△ [14p-B12-8] Thermal conductivity of the polycrystalline and epitaxial Al-doped ZnO (AZO) thin fillms
Keywords:Al-doped ZnO (AZO), dc magnetron sputtering, Thermal conductivity
Al-doped ZnO (AZO) thin films have attracted much attention as possible alternatives for In2O3-based transparent conductive oxide films such as Sn-doped In2O3 (ITO), because Zn element is aboundant, where the AZO films can have high optical transparency in visible region and high electrical conductivity. For the various thermal designs of electronic devices using AZO, the reliable thermophysical property data are required. In this study, the relationship between the thermal conductivities and the electrical conductivities of the polycrystalline and the epitaxial AZO films with c-axis orientation were investigated.
AZO films with a thickness of 200 nm were deposited on quarzt and c-plane sapphire substrates heated at 573K by dc magnetron sputtering using a AZO target (Al2O3: 3wt.%) and Ar-O2 gases. The O2 flow ratio was varied from 0 to 1.5%. The sputtering chamber was evacuated down to a pressure of less than 5.0×10-4 Pa. Electrical conductivity was analyzed by the Van Der Pauw method. The thermal diffusivity was analyzed using a front heating/front detection type picosecond pulsed light heating thermoreflectance system.
From the XRD analysis, it was confirmed that AZO films with c-axis orientation grew on quarzt and c-plane sapphire substrates. X-ray pole figures of all the AZO films on c-plane sapphire substrates show the hexagonal symmetry spots of ZnO (10 1). So the hetero-epitaxial growth was confirmed for all the films deposited on the c-plane sapphire. Thermal conductivity of the polycrystalline and the epitaxial AZO films was smaller than the previous study because of the difference in Al doping quantity. Also thermal conductivity carried by phonon increased with the electrical conductivities because of the decrease in grane size and Al doping concentration, etc.
AZO films with a thickness of 200 nm were deposited on quarzt and c-plane sapphire substrates heated at 573K by dc magnetron sputtering using a AZO target (Al2O3: 3wt.%) and Ar-O2 gases. The O2 flow ratio was varied from 0 to 1.5%. The sputtering chamber was evacuated down to a pressure of less than 5.0×10-4 Pa. Electrical conductivity was analyzed by the Van Der Pauw method. The thermal diffusivity was analyzed using a front heating/front detection type picosecond pulsed light heating thermoreflectance system.
From the XRD analysis, it was confirmed that AZO films with c-axis orientation grew on quarzt and c-plane sapphire substrates. X-ray pole figures of all the AZO films on c-plane sapphire substrates show the hexagonal symmetry spots of ZnO (10 1). So the hetero-epitaxial growth was confirmed for all the films deposited on the c-plane sapphire. Thermal conductivity of the polycrystalline and the epitaxial AZO films was smaller than the previous study because of the difference in Al doping quantity. Also thermal conductivity carried by phonon increased with the electrical conductivities because of the decrease in grane size and Al doping concentration, etc.