Direct observation of surface alloying and interface roughening: growth of Au on Fe(001)

Scanning tunneling microscopy studies on the growth of Au on Fe(001) are reported. A surface alloy is observed for submonolayer deposition ( <0.5 monolayer) at temperatures higher than 370 K. This surface-confined alloy demixes when it is covered with Au and in combination with imperfect layer-by-layer growth a rough interface consisting of Au islands in and Fe islands on the original Fe(001) substrate is created. A real-space high resolution study of this buried interface is possible because of the large difference in interlayer spacing between bcc Fe(001) and fcc Au(001).