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Dense restructuring of amorphous silicon network induced by non-bonded hydrogen
摘要： We con?rmed the presence of non-bonded hydrogens (NBHs) in hydrogenated amorphous silicon (a-Si:H) ?lms, using a combination of multiple techniques (Rutherford backscattering spectrometry/hydrogen forward scattering, Fourier-transform infrared spectroscopy-attenuated total re?ection, and thermal desorption spectrometry). The hydrogen e?usion pro?le of an a-Si:H ?lm with large amounts of NBHs was analyzed in detail. We report the e?ect of NBHs on band structure and electrical conductivity, and we present additional considerations for previous data on number density of silicon, optical bandgap, and vacancy size distribution [J. Non-Cryst. Solids 447, 207 (2016)]. The e?ect of NBHs on the a-Si network is explained by the “dense restructuring model”.
关键词： thermal desorption spectrometry,Rutherford backscattering spectrometry,hydrogenated amorphous silicon,non-bonded hydrogens,dense restructuring model,Fourier-transform infrared spectroscopy
更新于2025-09-09 09:28:46
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Effect of a-Si thin film on the performance of a-Si/ZnO-stacked piezoelectric energy harvesters
摘要： In this letter, we present the fabrication and characterization of a zinc oxide (ZnO)-based nanogenerator for piezoelectric micro-energy harvesting by combining thin films of amorphous silicon (a-Si) and ZnO. We utilized the a-Si thin film as an interlayer to assemble several a-Si/ZnO-stacked piezoelectric nanogenerators (SZPNGs) on indium tin oxide (ITO)-coated polyethylene naphthalate substrates. We investigated the influence of the a-Si layer thickness on the output voltages of the SZPNGs and demonstrated the existence of an optimal a-Si thickness for maximizing the output voltage. Overall, the SZPNGs generated higher output voltages than a conventional ZnO-based piezoelectric nanogenerator (ZPNG) lacking an a-Si interlayer, indicating enhanced performance. In particular, the SZPNG based on the optimal a-Si thickness exhibited a sixfold higher output voltage compared with the conventional ZPNG. This improved performance was ascribed to a combination of the Schottky barrier at the ITO/a-Si interface, preventing the screening effect and the relatively high dielectric constant (er≈13) of a-Si, minimizing the loss of the piezoelectric potential induced in the ZnO layer. The results herein are expected to assist the development of even more advanced ZnO-based piezoelectric nanogenerators in the future.
关键词： piezoelectric energy harvesting,zinc oxide,amorphous silicon,Schottky barrier,nanogenerator
更新于2025-09-04 15:30:14
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centers in amorphous
摘要： We investigate the charge-trapping behavior in nitrogen-deficient amorphous silicon nitride (a-Si3N4?x) using first-principles calculations. The amorphous ensembles with one nitrogen atom missing are generated through melt-quench procedures. The nitrogen deficiency mainly produces one Si—Si bond and one K center (Si dangling bond). The energy level of defect states indicates that the K centers act as possible trap sites. The transition levels of K centers are estimated, and it is found that the Hubbard U energy ranges from ?1.14 to 1.11 eV. Even though most K centers show positive U, the charge states of most centers in the ensemble are either positive or negative under the charge-neutrality condition, resulting in 'seemingly negative-U' behavior. This is consistent with the diamagnetic signal in experiments. The charge-injection energy of K centers is evaluated on the basis of the Franck-Condon approximation, and the average trap depths for electrons (1.33 eV below the conduction edge) and holes (1.54 eV above the valence edge) are in good agreement with experimental data.
关键词： K centers,Franck-Condon approximation,first-principles calculations,Hubbard U energy,amorphous silicon nitride,charge-trapping behavior
更新于2025-09-04 15:30:14