Influence Of Interfacial Roughness Research Articles

Influence of interfacial roughness on slot-die coatings for scaling-up high-performance perovskite solar cells

Slot-die coating (SDC) technology is a potential approach to mass produce large-area, high-performance perovskite solar cells (PSCs) at low cost. However, when the interface in contact with the perovskite ink has low wettability, the SDC cannot form a uniform pinhole-free perovskite film, which reduces the performance of the PSC. To address this issue, in this study, the wettability of the hole transport layer (HTL) interface was investigated in depth by analyzing the variation of wettability with process and its correlation with the roughness of the HTL interface. As a result, it was found that SDC could increase the roughness of the HTL interface to improve wettability and form a uniform high-quality perovskite layer without pinholes, and furthermore, SDC-based NiOx/Me-4PACz HTL suppressed energy losses at the HTL/perovskite interface. In addition, a unit cell achieved 19.17% of efficiency with long-term stability and lab cell-sized modules showed up to 17.42%.

Analysis of interfacial crack initiation mechanism of thermal barrier coatings in isothermal oxidation process based on interfacial stress state

In this paper, the interfacial stress state is used to analyze the interfacial crack initiation mechanism of the thermal barrier coatings (TBCs) during isothermal oxidation. The influence of thermal growth stress, initial residual stress, and creep behavior on the stress distribution is considered to have an accurate simulation result. A parameter that integrates the effects of interfacial normal and tangential stress is modified for evaluating interfacial crack initiation. It is found that, in the cooling stage, the interfacial cracks sprout at the top coat (TC)/thermally grown oxide (TGO) interface valley region and the TGO/bond coat (BC) interface peak region, which agrees with the experimental results. Furthermore, the influence of interfacial roughness on crack initiation is investigated. The result shows that different interfacial roughness affects the sprouting region of interfacial cracks and cracks within the TC layer.

Effect of Ti underlayer thickness on the magnetic anisotropy of TbFe thin films

In this study, we address the impact of Ti underlayer thickness (UL: 0-40 nm) on the structural, magnetic, and microscopic properties of TbFe thin films. The structural analysis confirmed the intermixing at interfaces of the Ti and TbFe layer with the increment of UL thicknesses. Out-of-plane (OOP) coercivity (\({H_{\rm{c}}}\)), and saturation field (\({H_{\rm{s}}}\)) gradually increased with an increase in UL thickness. For UL = 10 nm, the domain contrast and OOP stray field strength were enhanced, which may be due to the extent of d-d hybridization dominated over the influence of interfacial roughness. While for UL = 20, and 40 nm, the extent of interfacial roughness dominated the hybridization effects. In the case of UL: 20 nm, \({H_{\rm{c}}}\) increased by nearly 6 times more than the bare TbFe system. We observed a state with high OOP \({H_{\rm{c}}}\) combined with nearly zero OOP stray fields that are found to coexist in the sample. The magnetization reversal studies on a large area reveal domain nucleation followed by domain wall motion in all the films. The idea of tuning magnetic properties by varying thicknesses of Ti UL may be useful in spintronics applications.

Influence of interfacial roughness on exchange bias in core-shell nanoparticles

Exchange bias is a phenomenon that has attracted a great deal of interest in the 50 years following its discovery, but that is still lacking a deep theoretical understanding of its origin in core-shell nanoparticles. We present calculations of ferro-antiferromagnetic core-shell nanoparticles with roughened interfaces and demonstrate a wide dispersion in the calculated exchange-bias field caused by the roughening. Furthermore, we show that the magnitude of the exchange-bias field is strongly correlated with the net interfacial moment in the antiferromagnet, proportional to the degree of the interfacial roughness. This provides new insight into the origins of exchange bias in core-shell nanoparticles.

복합재료/금속 접착 계면의 혼합모드 파괴인성 측정

복합재료/금속 접착 조인트의 파손기준을 제시하기 위하여 다양한 혼합모드 하중상태에서 계면파괴인성을 측정하였다. 계면파괴인성은 SLB 시편을 이용하여 측정하였으며 시편의 두께를 변화시킴으로 모드 혼합비율을 다양하게 설정하였다. 실험결과 계면의 파괴인성은 균열 열림에 비해 균열 미끄러짐 모드의 비율이 높은 하중상태에서 더 큰 값을 나타내었다. 균열 열림 및 미끄러짐 하중모드에 따른 계면파괴 거동의 차이를 균열진전 과정을 관찰한 현미경 영상을 기초로 고찰하였다. 표면 거칠기가 접착 강도에 미치는 영향 또한 고찰되었다. Interfacial fracture toughness under various mixed-mode loading is measured to provide a mixed-mode fracture criterion of a composite/metal bonded joint. Experimental fracture characterization tests were carried out using a SLB (single leg bending) specimen, which controls mode ratio with the specimen thickness. The experimental result of the SLB test conforms that interfacial fracture toughness increases as the mode II component increases. The effect of loading mode on interfacial crack growth is investigated on the basis of crack path observation using microscopic image acquisition technique. The influence of interfacial roughness on adhesion strength is also discussed.

The influence of interfacial roughness on the coherence of structure and magnetic couplingacross barriers in Fe/MgO multilayers

Single-crystal Fe/MgO multilayers are model systems in which to study magnetic tunneljunctions. We find that the interfacial roughness leads to the loss of coherence of the crystalstructure. For thick MgO layers ferromagnetic (FM) ordering is found using polarizedneutron reflectivity (PNR). For thin MgO layers magnetization measurements reveal thepresence of antiferromagnetic (AF) interactions, but no long-range AF order is foundusing PNR. After cycling in a hysteresis loop, FM correlations are found at thecoercive point, and this will limit the maximum tunnelling magnetoresistance.

Real structure effects in X-ray waveguide optics: The influence of interfacial roughness and refractive index profile on the near-field and far-field distribution

We generalize the optical treatment of X-ray waveguides to index profiles of arbitrary shape. The modes of the waveguides are computed numerically by Numerov’s method. The method is first validated by considering profiles for which analytical solutions exist. Next, the effects of different shape functions and of interfacial roughness on the near and far-field intensity distributions are studied. The results are helpful to judge the real structure effects, e.g. resulting from fabrication imperfections, on the optical performance, as well as to optimize optical properties by designing generalized index profiles.

Influence of Interfacial Roughness on Fiber Sliding in Oxide Composites with La‐Monazite Interphases

Room‐temperature debonding and sliding of fibers coated with La‐monazite is assessed using a composite with a polycrystalline alumina matrix and fibers of several different single crystal (mullite and sapphire) and directionally solidified eutectic (Al2O3/Y3Al5O12 and Al2O3/Y‐ZrO2) compositions. These fibers provide a range of residual stresses and interfacial roughnesses. Sliding occurred over a debond crack at the fiber‐coating interface when the sliding displacement and surface roughness were relatively small. At large sliding displacements with relatively rough interfaces, the monazite coatings were deformed extensively by fracture, dislocations, and occasional twinning, whereas the fibers were undamaged. Dense, fine‐grained areas (10 nm grain size) resembling recrystallized microstructures were also observed in the most heavily deformed regions of the coatings. Frictional heating during sliding is assessed. Potential mechanisms for forming such microstructures at low temperature are discussed, and a parallel is drawn with the known resistance of monazite to radiation damage. The ability of La‐monazite to undergo both debonding and plastic deformation relatively easily at low temperatures may enable its use as a composite interface.

Influence of interfacial roughness on the tunnel magnetoresistance

The influence of interfacial roughness on tunnel conductance (TC) and magnetoresistance (TMR) are investigated taking into account spin–orbit (SO) coupling in ferromagnet (FM)/insulator (semiconductor) (I(S))/FM junctions. Explicit expressions for spin relaxation are obtained for ballistic and diffusive transport, respectively. The TC is expressed as the sum of different spin channels. Spin-flip (SF) scattering due to SO coupling is much stronger for antiparallel alignment of magnetization in the two FMs. The SF scattering cause a significant decrease of TMR ratio. We find that surface spin scattering predominates which suggests that the interfacial states play a key role in the tunnel process. The feature of the reduction of TMR changes with the disorder configuration and the SO coupling strength. Resonant TMR occurs due to the hopping between the SO-split energy levels.

A molecular dynamics investigation of a stepped metal-ceramic interface

Metal-ceramic interfacial systems play an important role in a wide variety of applications, from oxidation of metals and adhesion of protective coatings, to electronic packaging and structural composites. The understanding of the atomistic structural and dynamic response of such systems to external stresses is crucial to a full understanding of such phenomena as yield, fatigue, wear, and tribology. Molecular dynamics (MD) permits the controlled study of these systems at the atomistic level for relatively large numbers of atoms and complex geometries. In this paper, the influence of interfacial roughness on shear strength is considered. A model metal-ceramic interfacial system, subject to an external shear stress, is simulated using MD techniques. Periodic steps are placed in the interface to represent interfacial roughness. These steps are varied in relative metal/ceramic composition and step edge overlap.

The influence of interfacial roughness on parallel transport at oxide–semiconductor and heterojunction interfaces

Carrier scattering due to surface roughness at a nonideal interface may be an important mechanism in reducing carrier mobility and ultimately semiconductor device performance. We have investigated the role of this scattering mechanism in the low and high field transport of carriers parallel to oxide–semiconductor and heterojunction interfaces through analytic solutions and Monte Carlo simulation of the carrier dynamics. Quantitative differences between the scattering rates in the two types of systems arise from image potential contributions due to the presence of the dielectric in the oxide–semiconductor system which increases the scattering rate relative to a homogeneous system. For the InP/SiO2 system, surface scattering limits the surface channel mobility, even at room temperature. However, from detailed Monte Carlo simulation of high field transport in n-type InP inversion layers, we find that roughness scattering plays a relatively small role in reducing the peak and saturated carrier velocities since interface scattering is elastic and decreases with electron temperature. Thus, the short channel behavior in InP metal–oxide semiconductor field effect transistors may be comparatively better than that indicated by long channel results.