Gap states and recombination processes in one-dimensionally ordered and disordered a-Si : H/a-Si1−xNx:H multilayer films

1987 ◽  
Vol 97-98 ◽  
pp. 931-934 ◽  
Author(s):  
M. Yamaguchi ◽  
H. Ohta ◽  
C. Ogihara ◽  
H. Yokomichi ◽  
K. Morigaki ◽  
...  
1994 ◽  
Vol 339 ◽  
Author(s):  
L. Bergman ◽  
M. T. Mcclure ◽  
J. T. Glass ◽  
R. J. Nemanich

ABSTRACTMicro- and Macro-photoluminescence techniques were employed in this research to investigate the role of nitrogen-doping on the optical spectra of chemical vapor deposited diamond films and to determine whether the origin of the broadband luminescence is due to vibronic interaction of the nitrogen centers. The temperature behavior of the broadband PL and of the 1.681 eV silicon related optical center were analyzed. The intensity of the broadband was found to exhibit a temperature dependence characteristic of optical emission from a continuous distribution of gap states while the temperature dependence of the 1.681 eV band followed the Boltzmann quenching process.


1992 ◽  
Vol 258 ◽  
Author(s):  
Fan Zhong ◽  
J. David Cohen

ABSTRACTWe have applied the modulated photocurrent (MPC) method over a wide range of frequencies (5Hz-100kHz) and temperatures (120K-380K) to assess its ability to accurately deduce the mobility gap distribution in a-Si:H. We have also investigated the effects of moving both the Fermi level within some samples (by light soaking and partial annealing) and the quasi-Fermi level (by applying the bias light) to observe how such changes influence the deduced density of states (DOS). We then compared the MPC results directly with the DOS determined by junction capacitance measurements in the same sample devices. We have determined general conditions under which, we believe, the MPC results provide an accurate picture of the gap state distribution. However, we found that under other conditions, the appearance of the deep defect peaks and other features do not represent the actual defect distribution but, rather, are artifacts due to recombination processes.


1987 ◽  
Vol 95 ◽  
Author(s):  
R. B. Jones ◽  
G. Moddel

AbstractA method for determining the density of states [N(E)] in the upper half of the energy gap in hydrogenated amorphous silicon (a-Si:H) is proposed and experimental results are simulated. The method involves the growth and measurement of the planar conductivity in multilayer films in which each layer is separated by a thermally grown oxide. Band-bending occurs at each interface throughout the film thickness. The conductivity parallel to the layers in the films is a function of the band-bending, which in turn depends on N(E), in the energy range through which the Fermi level is shifted. Computer simulations of the oxide-induced band-bending have been used to generate curves of the conductivity as a function of layer-thickness for various N(E). By matching experimental results with the simulation curves, the N(E) may be deduced. The simulations have also been used to show the difference between the bulk conductivity activation energy and effective activation energy which is measured in films influenced by a surface oxide.


Author(s):  
Amanda K. Petford-Long ◽  
A. Cerezo ◽  
M.G. Hetherington

The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP) microanalysis without exposure to atmosphere) and onto the flat (001) surface of oxidised silicon wafers (for subsequent study in cross-section using high-resolution electron microscopy (HREM) in a JEOL 4000EX. Deposi-tion was from W filaments loaded with material in the form of wire (Co, Fe, Ni, Pt and Au) or flakes (Cr). The base pressure in the chamber was around 8×10−8 torr during deposition with a typical deposition rate of 0.05 - 0.2nm/s.


1997 ◽  
Vol 473 ◽  
Author(s):  
H. S. Yang ◽  
F. R. Brotzen ◽  
D. L. Callahan ◽  
C. F. Dunn

ABSTRACTQuantitative measurement of the adhesion strength of thin film metallizations has been achieved by a novel technique employing electrostatic forces to generate delaminating stresses. This technique has been used in testing the adhesion of Al-Cu, Cu, and Al multilayer films deposited on Si. Micro-blister-type failure is revealed by scanning electron microscopy. The delamination process and the geometry of the blister are discussed. The measured adhesion data fit a Weibull distribution function.


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