The superconducting properties of ultrathin films are directly related to their thickness according to new experimental results from physicists in China and the US. Qi-Kun Xue of the Chinese Academy of Sciences in Beijing and co-workers have found that the superconducting transition temperature of thin films made of lead varies with the number of atomic layers in the film (Y Guo et al. 2004 Science 306 1915).

Modern electronic devices are often made of thin films. According to the "particle-in-a-box" model of quantum mechanics, electrons confined in a perfectly uniform thin film are quantized into discrete energy levels known as quantum well states. The formation of these states can modify the distribution of electrons near the Fermi level, and therefore have an influence on the physical and chemical properties of the film.