Atomic Mating of Germanium Surfaces

Single crystals of germanium have been partially split in ultrahigh vacuum (∼10⁻⁹ Torr), and the surfaces of the split recontacted with high precision. Initially, an internal n‐p‐n structure appears about the mated split in n‐type specimens, indicating that the surfaces, although in intimate, possibly atomic, contact, retain their new surface structures sufficiently to trap electrons. Subsequently, portion of the junction disappears to an extent which varies from specimen to specimen. This is interpreted as due to the occurrence of atomic bonding across portion of the contacted region, and suggests that cleaved and annealed surface structures are not drastically different from ideal surfaces. When irradiated with a light spot the remaining junction region causes a photovoltage to appear which reverses in sign as the spot traverses the mated region. Due to the narrowness of the latter, applications as light detectors of high positional sensitivity are indicated. The p‐type specimens show no junctions when surfaces are mated, confirming that clean cleaved surfaces remain p type. Specimens (n or p) containing surfaces mated in air show no photovoltage. Specimens containing surfaces mated above 200°C, the cleaved‐to‐annealed surface transition temperature, appear to have higher photovoltages than those mated at room temperature.