ENTER THE OXIDES

摘要

In late 1996, a young Bell Labs physicist named Harold Hwang told his lab director that he wanted to start a radical programme of research into oxides - the ubiquitous, oxygen-bearing compounds found in everything from granite and glass to ceramics, chalk and rust. Hwang was convinced that even the most familiar oxides might show surprising and useful properties if different ones could be stacked up into 'heterostructures': layer-cake-like arrangements in which each level is an ultrathin film just a few atoms thick. rnThe lab director, Horst Stormer, was slightly dubious - not about the potential, but about the practicality. "Have you ever grown a thin film in your life?" he asked. He knew all too well what Hwang was getting himself into. Stormer had made his own reputation by growing and studying thin films of a very different class of materials: semiconductors. Those films had shown some remarkable properties - including a phenomenon called the fractional quantum Hall effect, in which the free-roaming electrons inside a layer condense into a liquid-like state. That discovery would later earn Stormer a share of the 1998 Nobel Prize in Physics. But such phenomena appeared only if the layers were absolutely uniform in height, with a crystalline structure that was so pure and defect-free that electrons could race along without crashing rninto imperfections.