Band offset at the heterojunction interfaces of CdS/ZnSnP₂, ZnS/ZnSnP₂, and In₂S₃/ZnSnP₂

Heterojunctions were formed between ZnSnP₂ and buffer materials, CdS, ZnS, and In₂S₃, using chemical bath deposition. The band offset was investigated by X-ray photoelectron spectroscopy based on Kraut method. The conduction band offset, ΔEC, between ZnSnP₂ and CdS was estimated to be -1.2 eV, which significantly limits the open circuit voltage, VOC. Conversely, ΔEC at the heterojunction between ZnSnP₂ and ZnS was +0.3 eV, which is within the optimal offset range. In the case of In₂S₃, ΔEC was a relatively small value, -0.2 eV, and In₂S₃ is potentially useful as a buffer layer in ZnSnP₂ solar cells. The J-V characteristics of heterojunction diodes with an Al/sulfides/ZnSnP₂ bulk/Mo structure also suggested that ZnS and In₂S₃ are promising candidates for buffer layers in ZnSnP₂ thin film solar cells, and the band alignment is a key factor for the higher efficiency of solar cells with heterojunctions

Observation on Behavior of Flowing Diriftwoods around Bridge Pier

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Detection of Neodymium-Rich Phase for Development of Coercivity in Neodymium-Iron-Boron-Based Alloys with Submicron-Sized Grains Using Positron Lifetime Spectroscopy

In order to evaluate the relationship between positron lifetime and microstructure, which contributes to the development of coercivity in hydrogenation-disproportionation-desorption-recombination (HDDR)-processed Nd-Fe-B-based alloys, detailed studies of positron lifetime spectroscopy were performed on HDDR-processed Nd-Fe-B-based alloys during desorption-recombination (DR) treatment. After the onset of coercivity, the change in positron lifetime closely corresponded to the change in intrinsic coercivity (H cJ ) with the progress of DR treatment. This result can be explained in terms of the grain size of the recombined Nd 2 Fe 14 B phases and the diffusion length of positrons, which annihilate in the matrix before reaching the grain boundary. Furthermore, positron lifetime spectroscopy was able to detect small changes in the grain boundary region very sensitively compared with thermal desorption spectroscopy (TDS) and X-ray diffraction (XRD). These changes in the grain boundary region caused the onset of coercivity attributed to the formation of Nd-rich intergranular phases. These results indicate that formation of a small amount of the Nd-rich intergranular phase during the DR process, which could be detected by positron lifetime spectroscopy, contributes to the onset of coercivity, even if NdH x phases remain

Role of Cu film texture in grain growth correlated with twin boundary formation

To understand the role of Cu film texture in grain growth at room temperature (RT) in relation to twin boundary formation Cu films were deposited on various barrier materials and the Cu film texture was investigated by X-ray diffraction. Cu grain growth was rapid on a barrierless SiO2/Si substrate and very slow on a Ta barrier due to strong (1 1 1) texture. The growth rate and the average grain diameter after being kept at RT for up to ∼60 days were maximum at a (2 0 0)Cu peak to (2 2 2)Cu peak area ratio of ∼1.0, where {1 1 1}, {1 0 0} and {5 1 1} grains coexisted. Such coexistence of three or more orientations of grains is essential in facilitating Cu grain growth at RT. Similarly, the average twin boundary (TB) density was maximum when Cu grain growth was facilitated. TB formation in nano-sized Cu grains was not controlled by grain size, but due to grain growth. The TB could be annealing twins caused by irregularities in the stacking sequence during relatively fast grain growth. The Cu film texture is concluded to be determined at the beginning of deposition, and the wettability of various barrier materials by the Cu films plays a key role in determining the film texture

Rutherford Backscattering Spectrometry Analysis of Self-Formed Ti-Rich Interface Layer Growth in Cu(Ti)/Low-k Samples

A new fabrication technique to prepare ultrathin barrier layers for nanoscale Cu wires was proposed in our previous studies. Ti-rich layers formed at Cu(Ti)/dielectric layer interfaces consisted of crystalline TiC or TiSi and amorphous Ti oxides. The primary control factor for the Ti-rich interface layer composition was C concentration in the dielectric layers rather than the formation enthalpy of the Ti compounds. To investigate Ti-rich interface layer growth in Cu(Ti)/dielectric layer samples annealed in ultrahigh vacuum, Rutherford backscattering spectrometry (RBS) was employed in the present study. Ti peaks were obtained only at the interfaces for all samples. Molar amounts of Ti atoms segregated to the interfaces (n) were estimated from Ti peak areas. Log n values were proportional to log t values. Slopes were similar for all samples, suggesting similar growth mechanisms. The activation energy (E) for Ti atoms reacting with the dielectric layers containing carbon (except SiO2) tended to decrease with decreasing C concentration (decreasing k), while those for the SiO2 layers were much higher. Reaction rate coefficients [Z · exp(−E/RT)] were insensitive to C concentration in the dielectric layers. These factors lead to the conclusion that growth of the Ti-rich interface layers is controlled by chemical reactions, represented by the Z and E values, of the Ti atoms with the dielectric layers, although there are a few diffusion processes possible