Papers - UMEZU Ikurou
-
STRUCTURE OF AMORPHOUS SINX-H STUDIED BY PHOTOEMISSION AND INFRARED-ABSORPTION
UMEZU, I, K MAEDA
JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 30 ( 10 ) 2547 - 2552 1991.10
Joint Work
Publisher：JAPAN J APPLIED PHYSICS
We present an X-ray photoemission (XPS) and infrared absorption (IR) study of hydrogenated amorphous silicon-nitride (SiNx:H) films which were prepared by plasma decomposition of SiH4 and NH3. Both Si 2p (XPS) and Si-H (IR) peaks are decomposed to contributions from Si-centered tetrahedrons. The peak shift in both XPS and IR can be divided into two compositional regions: below and above x = 1.0. Peak energy increases gradually with x until it reaches 1.0. For x > 1.0, the increment of peak shift is small. There are no particular features at around stoichiometric composition, x = 1.33. The kink point at around x = 1.0 and maximum composition of x = 1.7 are discussed in terms of Si-centered tetrahedrons. The Si-Si bond, which decreased with increasing source gas ratio R (R = [NH3]/[SiH4]), did not disappear even though a large gas ratio R was given. This feature is important in accounting for the structure of the films.
-
ATOMIC MICROSTRUCTURE AND ELECTRONIC-PROPERTIES OF A-SINX-H DEPOSITED BY RADIO-FREQUENCY GLOW-DISCHARGE
K MAEDA, UMEZU, I
JOURNAL OF APPLIED PHYSICS 70 ( 5 ) 2745 - 2754 1991.9
Joint Work
Publisher：AMER INST PHYSICS
a-SiN(x):H films of various composition x were deposited by rf glow discharge (GD). The deposition rate was analyzed for three ranges of gas flow ratio R = [NH3]/[SiH-4] depending on the deposition mechanism. Properties of these films were measured by means of x-ray photoelectron spectroscopy (XPS), infrared (IR) absorption, optical absorption, and the temperature dependence of electrical conductivity. The composition x was determined by XPS. For large values of R, x was found to be saturated at 1.7. The variation of H content was detected by IR absorption. The variation of coordinating atoms of Si with increasing x was deduced from the variation of XPS spectra of the Si 2p core-level and the shift of Si-H stretching vibration frequency in IR absorption. Based on the random bonding model and assuming bonding units to the central Si atom to be Si, N, and NH, probabilities of Si tetrahedra with various coordinating units were obtained. The results indicate that there are many Si-Si bonds for the stoichiometric x = 1.33 and that the concentration of Si-Si bonds diminishes at around the saturation value x = 1.7. These results seem to imply that the presence of Si-Si bonds to some extent is a prerequisite condition for film deposition by GD. Experimental results of optical absorption analyzed by Tauc relation revealed the presence of two kinds of x region whose properties are quite different. For x < 1.5, its optical absorption is similar to a-Si:H modified by the presence of N. With increasing x, the optical band gap E(O) increases and B coefficient in the Tauc plot decreases. At about x = 1.5, Si-Si bonding effectively disappears and the optical absorption abruptly changes to that similar to beta-Si3N4. Considering these results, the change of electronic band structure with x was deduced on the basis of the atomic structure obtained above and by the tight binding approximation. For x < 1.5, the optical band gap is due to Si-Si bonding, the energy gap of which increases, and the linear band tail becomes broad with increasing x. From the observed temperature dependence of conductivity, variations of the activation energy and pre-exponential factor are obtained with x up to x = 1.0. For the decrease of conductivity with x, the contribution from the pre-exponential factor is much larger than that from the activation energy. This result can be understood by a transport mechanism in the electronic band structure obtained above. Finally, it is concluded that the electronic properties of a-SiN(x):H deposited by GD ranging from semiconductor to insulator can be explained by the atomic microstructure and the electronic energy band structure.
-
NONIDEAL J-V CHARACTERISTICS AND INTERFACE STATES OF AN A-SI-H SCHOTTKY-BARRIER
K MAEDA, UMEZU, I, T YOSHIMURA, H IKOMA
JOURNAL OF APPLIED PHYSICS 68 ( 6 ) 2858 - 2867 1990.9
-
光音響法による非輻射遷移過程の研究
梅津郁朗
1990.3
Single Work
-
A comparative study of photoluminescence properties of a-SiOx:H film and silicon nanocrystallites（共著）
I. Umezu, K. Yoshida, A. Sugimura, T. Inokuma, S. Hasegawa, Y. Wakayama, Y. Yamada and T. Yoshida
- 1111.11
Joint Work
Authorship：Lead author
A comparative study of photoluminescence properties of a-SiOx:H film and silicon nanocrystallites