Stages Of Interdiffusion Research Articles

Stability of Interface Morphology and Thermal Boundary Conductance of Direct Wafer Bonded GaN|Si Heterojunction Interfaces Annealed at Growth and Annealing Temperatures

The properties of thin (~2 um) GaN templates on a silicon support substrate were studied to assess the stability of the direct wafer bonded GaN / Si interface. EVG® ComBond® equipment was used for bonding under high vacuum (~10-8 mtorr) at room temperature to remove unwanted native surface oxides [1,2]. For the bonded samples, the [1010] GaN edge was aligned parallel to the Si [110] edge. An X-ray diffraction reciprocal space map of the (004) Si and (0004) GaN revealed that there is a ~0.2° tilt between the GaN and Si layers and is simply due to the relative miscut between the two wafers. The treatment of the surfaces prior to bonding produces an amorphous region at the bonded interface that has been seen in many other bonded systems [3-5]. In the as-bonded sample, high resolution scanning transmission electron microscopy revealed a ~2 nm amorphous region on the Si side of the bonded interface, as confirmed by energy dispersive x-ray spectroscopy (EDX). Subsequent annealing was performed in an effort to recrystallize the amorphous interface. Previous work has shown that recrystallization between Si|Si wafer bonded samples occurred when annealed at 450 °C for 12 hours [3]. However, in the GaN|Si system, we found that the amorphous interface did not recrystallize when annealed under those conditions. Annealing at temperatures up to 450 °C and 120 hours showed only initial stages of interdiffusion and a stable interface. However, after annealing at 700 °C for 24 hours, high resolution EDX revealed the formation of amorphous SiN as well as the diffusion of gallium into silicon.Preliminary thermal results show that the thermal boundary conductance (TBC) of the as bonded sample is ~140 MW/(m2K). The TBC results of wafer bonded GaN|Si reported here is higher than previously reported TBC values of epitaxially grown interfaces such as GaN on Si [6], GaN on SiC [7], and GaN on diamond [8]. The TBC for the annealed interface is degraded by a factor of two compared to the as-bonded interface for the sample that was annealed at 700 °C for 24 hours. These results demonstrate that high TBC can be achieved through wafer bonding of GaN with materials such as silicon and that such interfaces are stable even up to device operation up to 300 °C. However, chemically rough interfaces formed due to high temperature annealing are detrimental to thermal transport across these interfaces. V. Dragoi, et al., ECS Trans., 86(5), 23 (2018)C. Flötgen, et al., ECS Trans., 64(5), 103 (2014)M.E. Liao, et al., ECS Trans., 86(5), 55 (2018)Y. Xu, et al., Ceramics International, 45, 6552 (2019)F. Mu, et al., Appl. Surf. Sci., 416, 1007 (2017)L. Yates, et al., ASME InterPACK (2015)J. Cho, et al., Phys. Rev. B, 89, 115301 (2014)H. Sun, et al., APL, 106(11), 111906 (2015) Figure 1

Kızılötesi Isıtma ile Polistiren Latekslerin Polimer Kompozit Filmlerindeki Film Oluşumuna Etkisi

This work presents a spectroscopic technique that film formation from polystyrene (PS)-polyacrylamide (PAAm) and polystyrene (PS)/Na-Alginate (Alg) composites was investigated using by UV-Visible technique. All samples were prepared at room temperature by casting methode on a glass substrate with different compositions of (PS)/polyacrylamide (PAAm) and polystyrene (PS)/Na- Alginate (Alg) films. Corresponding activation energies for the void closure and the interdiffusion stages were calculated of the films annealed by infrared heating. It was found that the calculated energies for the void closure processes smaller for the polystyrene (PS)/Na-Alginate (Alg) composite films than that of polystyrene (PS)/polyacrylamide (PAAm) composite films by infrared heating.

Mechanical and film formation behavior from PDMS/NaY zeolite composite membranes

ABSTRACTIn this study, polydimethylsiloxane (PDMS) and NaY zeolite doped composite membranes were prepared for the films varying from 0 to 15 NaY zeolite wt %. All the membranes were characterized by attenuated total reflectance–Fourier transform infrared (FTIR), X‐ray diffraction, scanning electron microscopy, thermogravimetry/differential thermal analysis methods. The FTIR spectral results showed that there is physical interaction existing between the PDMS matrix and NaY zeolite. Additionally, film formation from the pure PDMS and PDMS/NaY composites were investigated by photon transmission technique. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. The NaY zeolite added films led to the significant improvement in the mechanical properties that both the tensile strength and Young's modulus increased three times. Thermal properties of the films were also investigated and the addition of NaY zeolite into the PDMS matrix could significantly improve the thermal stability of the composite membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48549.

Monitoring the film formation process of polystyrene/poly acrylamide (PS/PAAm) composite films annealed by IR heating

In this study, UV‐visible (UVV) technique was used to probe the evolution of optical transmission during the film formation from composites of polystyrene (PS) latex particles and poly acrylamide (PAAm) films annealed by the infrared radiative heating (IRH) and convectional heating. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. It was shown that the activation energy for the void closure processes of viscous flow from the composite films decreased considerably in IRH annealing technique. It was observed that IRH heating speeds up the film formation process and the decrease the required energy. POLYM. ENG. SCI., 58:353–360, 2018. © 2017 Society of Plastics Engineers

Initial Stages of Interdiffusion between Asymmetrical Polymeric Layers: Glassy Polycarbonate and Melt Poly(methyl methacrylate) Interface Studied by Neutron Reflectometry

Interfacial evolution of deuterated polycarbonate (dPC) and poly(methyl methacrylate) (PMMA) bilayer films supported on silicon substrates was examined by neutron reflectometry. The dPC was in the glassy state and the PMMA was in the melt state when the samples were annealed at temperatures (from 400 to 415 K) between the bulk glass transition temperature (Tg) of dPC (Tg ∼ 418 K) and PMMA (Tg ∼ 390 K). Asymmetric concentration profiles were observed as a result of composition dependence of the mobility. Once the slow moving dPC molecules leave the dPC-rich side (which was glassy) and enter the PMMA side, the dPC molecules become fast moving and diffuse freely in a viscous melt environment, while the fast moving PMMA molecules become slow as PMMA enter the glassy dPC matrix. Slight change in molecular mass of dPC gives rise to remarkable difference in concentration profile, indicating that mutual diffusion is very sensitive to molecular friction and entanglement of medium. With the penetration of PMMA into the dPC-rich side, the sluggish relaxation of dPC with high molecular mass results in the swelling of the dPC layer.

Polymer/carbon nanotube composite film formation: A fluorescence study

In this study, the effect of multi‐walled Carbon nanotube (MWNT) on film formation behavior of Polystrene (PS) latex film was investigated by using steady state fluorescence technique. Films were prepared by mixing of pyrene (P)‐labeled PS latex with different amounts of MWNTs varying in the range between 0 and 20 wt%. After drying, MWNT containing films were separately annealed above glass transition temperature (Tg) of PS ranging from 100 to 270°C for 10 min. In order to monitor film formation behavior of PS/MWNT composites, Scattered light (Is) and fluorescence intensities (IP) from P were measured after each annealing step to monitor the stages of film formation. At 0–20 wt% range of MWNT content films, minimum film formation (To), void closure (Tv), and healing, (Th) temperatures were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that while void closure activation energies increased, backbone activation energies decreased as the percent of MWNT is increased in the composite films. POLYM. COMPOS., 35:817–826, 2014. © 2013 Society of Plastics Engineers

Film formation of nano‐sized hard latex (PS) in soft polymer matrix (PBA): An excimer study

AbstractThis work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)‐labeled nano‐sized polystyrene (PS) and poly(n‐butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (Tg) of polystyerene. Monomer (IP) and excimer (IE) intensities from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, Itr. Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component (PS) in the blend is decreased, a significant change occurred in both IE/IP and Itr curves at a certain critical weight fraction (50 wt%) of PS hard latex. Two distinct film formation stages, which are named as void closure and interdiffusion were seen in (IE/IP) data above this fraction. However, below 50 wt% PS no film formation was observed. AFM pictures also confirmed these findings. Void closure and interdiffusion stages for (50–100) wt% range of PS were modeled and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition in this range. POLYM. COMPOS., 31:1611–1619, 2010. © 2009 Society of Plastics Engineers

Poly (styrene) latex/modified Na-activated bentonite nanocomposite films: A fluorescence study

We studied film formation of composites of surfactant-free polystyrene (PS) nanoparticles and modified Na-activated bentonite (MLB), by steady state fluorescence (SSF) technique. The films were prepared from a mixture of pyrene (P)-labeled PS particles and MLB at various compositions at room temperature. These films were annealed at elevated temperatures above the glass transition ( T g) temperature of polystyrene for 10 min. Scattered light ( I s) and fluorescence intensities ( I P) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of the composite films was monitored by using photon transmission intensity, I tr. Atomic force microscopy (AFM) was used to detect the variation in physical structure of annealed composite films. The nanocomposite films exhibited a percolation threshold at 20 wt.% MLB content. Below this fraction two distinct film formation stages were observed which are known as void closure and interdiffusion and above this fraction no film formation was detected. At 0–20 wt.% MLB, minimum film formation, T 0, void closure, T v and healing, T h temperatures were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. Void closure activation energies decreased as the percent of MLB increased, no variation was observed in backbone activation energies.

Film formation from TiO2-polystyrene latex composite: a fluorescence study

This work reports the use of the steady state fluorescence (SSF) technique for studying film formation from TiO2 covered polystyrene (PS) latex particles. The composite films were prepared from pyrene (P)-labeled PS particles by covering them with TiO2 at room temperature and then annealed at elevated temperatures in 10 min time interval above glass transition (T g) temperature of polystyrene. Five different composite films were studied in various TiO2 layer contents. Fluorescence intensities I P from P were measured after each annealing step to monitor the stages of film formation. Films showed considerable increase in I P above the certain onset temperature called minimum film forming temperature, T 0. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 23.12 and 92.80 kJ mol−1, respectively.

The effect of clay particles on film formation from polystyrene latex

AbstractFilm formation from surfactant‐free polystyrene (PS) latex was performed in the presence of 5% Na‐montmorillonite (NaMMT). The composite films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures above the glass‐transition (Tg) temperature of polystyrene. Scattered light (Is) and fluorescence intensity (IP) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T0, and healing temperatures, Th, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities. POLYM. COMPOS., 27:299–308, 2006. © 2006 Society of Plastics Engineers

Chemical Composition of Advanced Materials as Obtained by the 3-Dimensional Atom Probe

The 3-dimensional atom probe is based on field ion microscopy where the screen is replaced by a 2-dimensional, position sensitive detector. Atoms were removed from a conducting sample by a high voltage pulse. The time of flight reveals their chemical nature, and continuous stripping allows lateral and in-depth analysis. The spatial resolution permits a chemical analysis on the sub-nanometer scale. Results of this new technique are presented for (i) the initial stages of interdiffusion at the boundary between two metals, (ii) P-segregation at grain boundaries in nanocrystalline Ni-P alloys, (iii) initial stages of nucleation and growth in various alloys, (iv) composition of thin oxide films in TMR-structures, and (v) distribution of hydrogen in metallic multilayers. It will be also shown that the new technique not only allowed a characterization on the atomic scale but verified and/or falsified existing models for the examples given before.

Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t3) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (Is) and fluorescence intensity (Ip) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, Itr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, Tq, and healing temperatures, Th, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.

X-ray investigation of quantum well intermixing after postgrowth rapid thermal processing

In order to better understand interdiffusion in quantum well based optoelectronic AlxGa1−xAs/GaAs devices, we have performed rapid thermal processing on similar periodic superlattices (SLs) grown by solid source molecular beam epitaxy. The interdiffusion has been studied by x-ray diffraction measurements. The intermixing of the atoms at the barrier–well interfaces in the temperature range between 800°C and 950°C shifts the energy levels of the bound states and thus the photoluminescence wavelength of the structures. X-ray ω–2θ scans confirm Al–Ga interdiffusion at the barrier–well interfaces and are quantitatively investigated by fitting the envelope function of the SL satellites. A fit to the data yields diffusion lengths in the range 0.2–2.7 nm. Diffusion coefficients and activation energies can be derived from the temperature dependence of diffusion lengths. In the samples that exhibit rougher interfaces, the early stages of interdiffusion at up to 800°C for 1 min show the narrowing and increasing of satellite peak intensities followed by their broadening and decrease of peak maxima at higher temperatures above 850°C. The observation correlates with the initial smoothing of the interfaces

Fluorescence study on Al2O3-polystyrene latex composite film formation

This work reports a steady state fluorescence (SSF) technique for studying film formation from mixture of Al2O3 and polystyrene (PS) latex particles. The composite films were prepared from dispersion of pyrene (P)-labeled PS particles in Al2O3 solution at room temperature and annealed at elevated temperatures in 10-min time interval above glass transition (Tg) temperature of polystyrene. Nine different composites film were studied in various latex contents. Fluorescence intensities (IP) from P were measured after each annealing step to monitor the stages of film formation. No variations in IP were detected for the films prepared with higher than 33 wt% Al2O3 content. However films prepared below 33 wt% Al2O3 content show considerable increase in IP above the certain onset temperature called minimum film forming temperature, T0. Healing temperatures Th, were determined from the maxima of IP. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 20 and 97 kJ.mol–1, respectively. POLYM. COMPOS., 26:352–360, 2005. © 2005 Society of Plastics Engineers

Film formation from nano-sized polystyrene latex particles

This work reports on the steady state fluorescence (SSF) technique for studying film formation from surfactant-free, nano-sized polystyrene (PS) latex particles prepared via emulsion polymerization. The latex films were prepared from pyrene (P)-labeled PS particles at room temperature and annealed at elevated temperatures in 5, 10, 15, 20 and 30 min time intervals above the glass transition temperature (Tg) of PS. During the annealing processes, the transparency of the film was improved considerably. Monomer and excimer fluorescence intensities, IP and IE respectively, from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of the latex films was monitored by using photon transmission intensity, Itr. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 10.3 and 50.3 kJ mol−1. Void closure temperatures, Tv, were determined from the minima of Itr value. Copyright © 2005 John Wiley & Sons, Ltd.

Film formation from surfactant-free, slightly crosslinked, fluorescein-labeled polystyrene particles

A steady state-fluorescence (SSF) technique for studying film formation from surfactant-free, slightly crosslinked polystyrene (PS) latex particles is reported. The powder films were prepared from fluorescein (F)-labeled PS particles at room temperature. The mechanically strong films were obtained by annealing these films at elevated temperatures in 5, 10, 20, and 30 min time intervals above the glass transition (Tg) temperature of polystyrene. Scattered light (Is) and fluorescence (IF) intensities from F were monitored after each annealing step to investigate the three different film formation stages called void closure, healing, and interdiffusion. The evolution of transparency of the latex films was monitored by using a photon transmission technique. Scanning electron microscopy (SEM) was employed to detect the variation in physical structure of the annealed latex films. Onset temperature for void closure, Tm’, and healing temperatures, Th, were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were also modeled and the related activation energies were also determined. It was observed that lower energy is needed for the void closure process than interdiffusion of chains across the particle-particle boundaries.

Void closure and interdiffusion processes during latex film formation from surfactant-free polystyrene particles: a fluorescence study

This study reports a steady state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex particles. The latex films were prepared from pyrene (P)-labeled PS particles at room temperature and annealed at elevated temperatures for 5-, 10-, 20-, and 30-min time intervals above the glass transition ( T g) temperature of polystyrene. During the annealing processes, the transparency of the film changed considerably. Scattered light ( I sc) and fluorescence intensity ( I 0P) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of latex films were monitored using photon transmission intensity, I tr. Scanning electron microscopy (SEM) was used to detect variation in the physical structure of annealed films. Onset temperature for film formation, T 0, void closure, T v, and healing temperatures, T h, were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were modeled and related activation energies were determined.

Interdiffusion and reaction of metals: The influence and relaxation of mismatch-induced stress

The early interdiffusion stages in epitaxially grown Ag/Au and Cu/Au reaction couples are investigated by high-resolution and Z-contrast electron microscopy. While the interdiffusion in the lattice-matched system Ag/Au follows Fick's diffusion laws from the very beginning, a complex two-stage reaction is observed in the lattice-mismatched Cu/Au samples. A fast diffusion at the beginning of the heat treatment produces a planar zone of lattice defects along the interface, which release most of the induced stress. This first reaction stage stops after reaching a diffusion length of about 15 nm. Subsequent interdiffusion takes place by a recrystallization mechanism comprising heterogeneous nucleation of new grains and diffusion-induced grain boundary migration. During this second reaction stage, discontinuous composition profiles are determined, evidencing stress release at high-angle grain boundaries. The recrystallization mechanism also dominates the formation of ordered intermetallics at lower reaction temperatures.

Chemical analysis by high-angle hollow cone illumination

The high-angle hollow cone illumination realized in a conventional transmission microscope is known to suppress coherent contrast mechanisms. It is shown that under suitable experimental conditions, orientation and strain contrasts are sufficiently suppressed to obtain a Z-contrast image. Various factors, influencing the image intensity, are determined by a quantitative image analysis of pure metals. Based on these measurements an incoherent multiscattering model is generalized to binary alloys in order to describe the chemical image contrast and to determine the local composition of the specimen from an intensity measurement. To test the concept, the early stages of interdiffusion between thin films of Cu and Au are investigated. The results demonstrate that a useful chemical analysis is possible, even in the case of nanocrystalline specimens. Complete composition profiles are determined on a length scale of 10 nm. The spatial and chemical resolution of the method are discussed.

Effects of confined geometry and substrate interaction on the initial stages of interdiffusion in polystyrene films

The effects of confined geometry and substrate interaction on the short time interdiffusion in polymer films have been investigated by neutron reflectometry. Samples consist of alternating layers of protonated and deuterated polystyrene. The interface broadening of a thick film (4.4 R g thick) confined between two thick films, a thinner film (0.78 R g thick) confined between two thick ones and a thin film (0.77 R g thick) deposited directly on a glass substrate with a thick film on top is measured as a function of time. R g is the bulk radius of gyration, which is taken as a measure of the relative film thickness compared to the chain dimension. Samples are subsequently annealed at temperatures slightly above the glass transition temperature, T g, and the interface widths as a function of time are determined from model fits to neutron reflectivity curves. Neither a relaxation process at small times nor a large change of segmental dynamics as a function of film thickness are observed. Only a slowing down of interdiffusion dynamics for the thin film between two thicker ones is detected as well as a still smaller interdiffusion for the thin film placed directly on the substrate, which is attributed to polymer–substrate interaction.