A focused He+ beam with a beam diameter less than 1 nm is heating up the targeted surface for a He+ dose larger than 1 × 1020 ions cm-2. The temperature can reach 1000 °C locally, resulting in surface decomposition or chemical reactions. This temperature was measured by fabricating gold nanodisks down to 20 nm in diameter and 10 nm in thickness on mica and sapphire surfaces. The melting and vaporization of these nanodisks were used to determine this temperature according to the known gold nanocluster melting temperature variations as a function of their volume. This local heat production is very negative for precise He+ nanolithography resist processes but advantageous without a resist when used to directly nano-sculpture a nanomaterial when a very thermally conductive support like sapphire is selected.