Size dependence of thermoelectric power of Au nanoclusters with rough and smooth surface deposited onto highly oriented pyrolytic graphite

•New contact-free technique for recovering of thermopower of nanoclusters is presented.•Thermopower of rough shaped Au nanolusters was found to decrease with decreasing of their sizes.•For rough shaped Au nanolusters of volume 0.1nm3 the recovered thermoelectric power value is −60μV/K.•Smooth shaped nanoclusters do not reveal the dependence of thermoelectric power on their size. The paper presents the analysis of tunnel current–voltage characteristics of gold nanoclusters deposited onto the highly oriented pyrolytic graphite (HOPG) surface by pulsed laser deposition. An original technique is suggested which allows recovering of the thermoelectric power value of nanoclusters by analyzing their differential tunneling current–voltage characteristics. It was found that the value of the thermoelectric power of pulsed laser deposited Au nanoclusters decreases with decreasing of their size down to −60μV/K for cluster's volume of 0.1nm3. At the same time the thermoelectric power value of thermal evaporated Au nanoclusters which have smooth surface does not reveal the size dependence for clusters with volume down to 0.5nm3. The analysis of the results and the possible causes of this behavior are discussed.