N-doped Surface Research Articles

Photoelectron emission from nitrogen- and boron-doped diamond (100) surfaces

The nitrogen-doped (N-doped), type Ib, synthetic diamond (100) surface was investigated by means of X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Photoelectron emission data from the boron-doped (B-doped) and the N-doped diamond (100) surfaces were compared and permitted the energy band diagrams for these differently terminated surfaces to be drawn. We observed emission from energy levels below the conduction band minimum up to the vacuum level and therefore succeed in evaluating the negative electron affinity (NEA) of the hydrogen-terminated diamond surfaces. Both the hydrogen-terminated N- and B-doped diamond (100) surfaces show NEA values of at least −0.2 and −1.0 eV, respectively, while the hydrogen-free surfaces show positive electron affinity. In contrast to the hydrogen-terminated B-doped (100) surface, UPS measurements on the hydrogen-terminated N-doped (100) surface do not reveal a high intensity NEA peak owing to the strong upward band bending. The high intensity NEA peak of B-doped diamond seems to be due to the downward band bending together with the reduced work function because of hydrogen termination. The work function increases for subsequent hydrogen desorption at higher annealing temperatures with associated loss of NEA. For the N-doped diamond (100) surface the work function behaves similarly but the observation of a NEA peak is absent because of the surface barrier formed by the upward band bending.

Step smoothing and surface vacancy reactions on InP(110) and GaP(110) observed by scanning tunneling microscopy

Abstract Tip-induced reactions changing the structure and electronic states of steps and vacancies through local mass transport on cleaved InP(110) and GaP(110) surfaces were studied by STM. Steps one atomic layer high on n-doped surfaces showed a progressive smoothing of step edges during continuous scanning. On the flat part of the surfaces point defects were created under the same experimental conditions and were identified as vacancies and vacancy clusters. Single P vacancies were converted into double vacancies, which were found to be the most stable configuration induced on n-doped surfaces under the influence of scanning, while on p-doped material single vacancies were stable. The double vacancies could, however, change reversibly under scanning into a new defect consisting of four vacancies with a triangular structure.

Step smoothing and surface vacancy reactions on InP(110) and GaP(110) observed by scanning tunneling microscopy

Tip-induced reactions changing the structure and electronic states of steps and vacancies through local mass transport on cleaved InP(110) and GaP(110) surfaces were studied by STM. Steps one atomic layer high on n-doped surfaces showed a progressive smoothing of step edges during continuous scanning. On the flat part of the surfaces point defects were created under the same experimental conditions and were identified as vacancies and vacancy clusters. Single P vacancies were converted into double vacancies, which were found to be the most stable configuration induced on n-doped surfaces under the influence of scanning, while on p-doped material single vacancies were stable. The double vacancies could, however, change reversibly under scanning into a new defect consisting of four vacancies with a triangular structure.

Electrical performance and Raman scattering characterization of GaAs planar photoconductors

Raman scattering has been used to characterize the effects of processing techniques on the photosensitive area of GaAs planar photoconductors. The longitudinal optic (LO) phonon observed in the first-order Raman spectra was studied to probe the consequences of both chemical and plasma etching on the crystalline quality of an n-doped GaAs photosentitive area. This method has also been used to examine the stress at the interface of a Si3N4 film and an n-doped GaAs surface. For this purpose, three specially designed GaAs planar photoconductors (SN 353, AN 344, SN 344) have been fabricated. Electrical measurements on the photoconductors support the results of Raman study. First, as expected, increasing the number of processes leads to slightly poorer electrical performance. Secondly, a significant strain-induced shift in the GaAs LO phonon frequency has been observed under the Si3N4 film for the AN 344 photoconductor. However, the electrical performances of this device clearly indicate no dramatic change in the value of the n-doped surface potential.

Capacitance spectroscopy of localized states at metal-semiconductor interfaces. II. Experiments about Ag, Au, and Ni on crystalline (111) Si surfaces

Metal-(111) silicon interfaces obtained by electron gun evaporation onto a clean cleaved n-doped Si surface are studied at various constant temperatures by small-signal capacitance measurement under both forward and reverse bias. The model described in the previous paper is applied and the slopes of the logarithmic capacitances or their cutoff frequencies versus junction voltage generally take the integer values which were estimated before. Moreover, these results bear out the identity of the quasi-Fermi level of electrons in the neutral region and near the interface. Thus a spectroscopy of the interface states is possible and results are interpreted owing to the model of the preceding paper. Both recombinations with the metallic electrons and the silicon holes are found, respectively, in Ni/Si and Ag/Si interfaces. Each interface shows distinct features which are tentatively correlated to the interface physical nature and metals band structures.