The recent development of new advanced materials demands extensive effort in developing new analytical techniques that can provide insight into material composition at the nanoscale, particularly at surfaces and interfaces, which is important for both fabrication and material performance. Here, we present a proof of principle for a new setup used for thin-film characterisation and depth profiling based on a combination of time-of-flight elastic recoil detection analysis (TOF-ERDA) and Ar sputtering. A quantitative depth profiling with a best achievable surface depth resolution of ~2 nm can be realised for the entire layer, which is important for the precise determination of thickness and composition of samples that are several tenths of a nanometre thick. The performance of TOF-ERDA with Ar sputtering was demonstrated using 15 nm Cu evaporated onto a Si substrate. The advantages and limits of the method are discussed in detail.