Gaudart L, Rivoira R
Appl Opt. 1971 Oct 1;10(10):2336-43. doi: 10.1364/AO.10.002336.
Thin films of calcium were evaporated under ultrahigh vacuum conditions (pressures less than 5 x 10(-10) Torr) onto quartz substrates to a thickness of 20 nm. The photoelectric yield and hence the work function of the layers were determined as a function of thickness. For film thicknesses greater than 10 nm, the work function was constant with a value of 2.87 +/- 0.06 eV. The work function suows minima at film thicknesses of about 2.5 nm and 5.5 nm. Results from films thicker from 5.5 are a good fit to the Fowler function; for thinner films, the results suggest the existence of a second photoelectric threshold with a corresponding work function ø(s). A theory based on the energy states of the surface electrons is proposed to explain both this second threshold and the ir absorption of thin calcium films.
在超高真空条件（压力小于5×10⁻¹⁰托）下，将钙薄膜蒸发到石英衬底上，厚度达到20纳米。测定了这些层的光电产额以及功函数随厚度的变化关系。对于厚度大于10纳米的薄膜，功函数恒定，值为2.87±0.06电子伏特。功函数在薄膜厚度约为2.5纳米和5.5纳米时出现最小值。厚度大于5.5纳米的薄膜的结果与福勒函数拟合良好；对于更薄的薄膜，结果表明存在第二个光电阈值以及相应的功函数ø(s)。提出了一种基于表面电子能态的理论来解释这个第二个阈值以及薄钙膜的红外吸收。
