Number Of Deposition Cycles Research Articles

High-Performance Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors Fabricated by Atomic Layer Deposition

This letter reports the fabrication of high-performance amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) via atomic layer deposition at a substrate temperature of 250 °C. The film thickness of In2O3, Ga2O3, and ZnO varied linearly with the number of deposition cycles. The cation composition of the IGZO film was controlled by an alternate stacking of In2O3, Ga2O3, and ZnO atomic layers. The fabricated a-IGZO TFTs exhibited a high electron mobility of 22.1 cm2/Vs, threshold voltage of 2.41 V, subthreshold gate swing of 0.30 V/decade, and an ${I}_{{ \mathrm{\scriptscriptstyle ON}}/{ \mathrm{\scriptscriptstyle OFF}}}$ ratio of $> \textsf {1} \times \textsf {10}^{\textsf {8}}$ .

Development of a Post-CMOS Compatible Nanoporous Thin Film layer Based on Al2O3

Porous alumina is a popular material with numerous application fields. A post-CMOS compatible process chain for the fabrication of nanoporous surface based on Al2O3 by atomic layer deposition (ALD) is presented. By alternately applying small numbers of ALD cycles for Al2O3 and ZnO, a homogenous composite was accomplished, for which the principle of island growth of ALD materials at few deposition cycle numbers was utilised. By selective texture-etching of ZnO content via hydrofluoric acid (HF) in vaporous phase at 40 °C and 10.67 mbar, a porous surface of the etch resistant Al2O3 could be achieved. TOF-SIMS investigations verified the composition of ALD composite, whereas AFM and high resolution SEM images characterised the topographies of pre- and post-etched samples. Pores with opening diameters of up to 15 nm could be detected on the surface after vaporous HF treatment for 2 minutes. The amount of pores increased after an etching time of 5 minutes.

Study of the physical properties of CuO thin films grown by modified SILAR method for solar cells applications

CuO has attracted much interest owing to its appropriate material properties, inexpensive fabrication cost and potential applications including energy devices. In this study, copper oxide CuO thin films were deposited on glass slides substrates by the simple and economical modified successive ionic layer adsorption and reaction (modified SILAR). Properties of synthesized films were studied as a function numbers of deposition cycles and immersion time in the anionic solution (reaction time). The structural, surface morphology, chemical compositions and optical properties of the films have been investigated by X-ray diffraction analysis, scanning electron microscopy SEM, EDX and UV-vis spectrophotometry.

High‐Purity Inorganic Perovskite Films for Solar Cells with 9.72 % Efficiency

AbstractAll‐inorganic perovskite solar cells with high efficiency and improved stability are promising for commercialization. A multistep solution‐processing method was developed to fabricate high‐purity inorganic CsPbBr3 perovskite films for use in efficient solar cells. By tuning the number of deposition cycles (n) of a CsBr solution, the phase conversion from CsPb2Br5 (n ≤3), to CsPbBr3 (n=4), and Cs4PbBr6 (n≥5) was optimized to achieve vertical‐ and monolayer‐aligned grains. Upon interfacial modification with graphene quantum dots, the all‐inorganic perovskite solar cell (without a hole‐transporting layer) achieved a power conversion efficiency (PCE) as high as 9.72 % under standard solar illumination conditions. Under challenging conditions, such as 90 % relative humidity (RH) at 25 °C or 80 °C at zero humidity, the optimized device retained 87 % PCE over 130 days or 95 % over 40 days, compared to the initial efficiency.

High-Purity Inorganic Perovskite Films for Solar Cells with 9.72 % Efficiency.

All-inorganic perovskite solar cells with high efficiency and improved stability are promising for commercialization. A multistep solution-processing method was developed to fabricate high-purity inorganic CsPbBr3 perovskite films for use in efficient solar cells. By tuning the number of deposition cycles (n) of a CsBr solution, the phase conversion from CsPb2 Br5 (n ≤3), to CsPbBr3 (n=4), and Cs4 PbBr6 (n≥5) was optimized to achieve vertical- and monolayer-aligned grains. Upon interfacial modification with graphene quantum dots, the all-inorganic perovskite solar cell (without a hole-transporting layer) achieved a power conversion efficiency (PCE) as high as 9.72 % under standard solar illumination conditions. Under challenging conditions, such as 90 % relative humidity (RH) at 25 °C or 80 °C at zero humidity, the optimized device retained 87 % PCE over 130 days or 95 % over 40 days, compared to the initial efficiency.

In-situ multi-deposition process for cobalt-sulfide synthesis with efficient bifunctional catalytic activity

ABSTRACTUniform CoS thin films were deposited by an in-situ multi-deposition method using cobalt nitrate as cationic source and sodium sulfide as anionic source. Influence of deposition cycle numbers was studied systematically by XRD and SEM. The thin film become smoothly and compactly with increase of deposition cycles to 4, and it agglomerated seriously when up to 8 cycles. The resultant sample exhibit outstanding bifunctional electrochemical catalytic properties for oxygen evolution and oxygen reduction (OER and ORR, respectively) for 4 deposition cycles in alkaline medium. The CoS exhibit low overpotential of 0.43 V to achieve 10 mA/cm2 for its OER activity. The CoS thin film for 4 dip-cycles has exhibited good performance with the half-wave potential of 0.7 V vs. RHE.

Ultrathin ALD TiO2 shells for enhanced photoelectrochemical solar fuel generation

ZnO/TiO2 core/shell heterojunction arrays were fabricated via the atomic layer deposition (ALD) of various ultrathin TiO2 layers on hydrothermally-synthesized hexagonal ZnO micro/nanorods. Current-voltage (I-V) characteristics of the photoanodes made using 10–75 cycles of TiO2 showed significant suppression in the dark current. Specifically, the sample made of 50 ALD cycles of TiO2 exhibited a 45% decrease in the dark current compared to the bare ZnO electrodes. Further increase in number of deposition cycles resulted in stability deterioration. The decay time constant measurements revealed electron lifetimes in the core/shell electrodes that are longer than those in pristine ZnO electrodes. Finally, Mott−Schottky analysis and the positron annihilation measurements confirmed the decrease in the donor density and surface defects for the core/shell electrodes. The results attained in this study represent a step towards a facile method to stabilize ZnO photoanodes from photodeterioration under the harsh operating conditions of water splitting.

Surface engineering of zirconium particles by molecular layer deposition: Significantly enhanced electrostatic safety at minimum loss of the energy density

Because of its high volumetric heat of oxidation, Zr powder is a promising high energy fuel/additive for rocket propellants. However, the application of Zr powder is restricted by its ultra-high electrostatic discharge sensitivity, which poses great hazards for handling, transportation and utilization of this material. By performing molecular layer deposition of polyimide using 1,2,4,5-benzenetetracarboxylic anhydride and ethylenediamine as the precursors, Zr particles can be uniformly encapsulated by thin layers of the polymer. The thicknesses of the encapsulation layers can be precisely controlled by adjusting the number of deposition cycle. High temperature annealing converts the polymer layer into a carbon coating. Results of thermal analyses reveal that the polymer or carbon coatings have little negative effect on the energy release process of the Zr powder. By varying the thickness of the polyimide or carbon coating, electrostatic discharge sensitivity of the Zr powder can be tuned in a wide range and its uncontrolled ignition hazard can be virtually eliminated. This research demonstrates the great potential of molecular layer deposition in effectively modifying the surface properties of highly reactive metal based energetic materials with minimum sacrifices of their energy densities.

Growth mechanism of Al2O3 film on an organic layer in plasma-enhanced atomic layer deposition

Differences in the physical and chemical properties of Al2O3 films on a Si wafer and a CxHy layer were investigated in the case of plasma-enhanced atomic layer deposition. The Al2O3 film on the Si had a sharper interface and lower thickness than the Al2O3 film on the CxHy. The amount of carbon-impurity near the interface was larger for Al2O3 on the CxHy than for Al2O3 on the Si. In order to understand these differences, the concentrations of Al, O, C, and Si atoms through the Al2O3 films were evaluated by using x-ray photoelectron spectroscopy (XPS) depth profiling. The emission intensities of CO molecule were analyzed for different numbers of deposition cycles, by using time-resolved optical emission spectroscopy (OES). Finally, a growth mechanism for Al2O3 on an organic layer was proposed, based on the XPS and OES results for the Si wafer and the CxHy layer.

A highly conducting flower like Au nanoparticles interconnected functionalized CNFs and its enhanced electrocatalytic activity towards hydrazine through direct electron transfer

Abstract A numerous number of carbon-based nanomaterials have been developed for various technological applications, nevertheless a degree of accessibility is very less. Notably, carbon nanofibers (CNFs) based materials are insufficiently studied compare to CNT and graphene due to their inaccessibility in aqueous dispersion. Here we have functionalized the CNF by using acid treatment for further modification. Functionalization of CNF was confirmed by different characterization techniques like FT-IR, RAMAN, and XRD. To increase the electrical conductivity of F-CNFs, flower-like Au nanoparticles were electrodeposited onto the F-CNFs. Optimization study for electrodeposition of Au nanoparticles was performed with Au precursor's concentration and deposition cycle number. As the result, the optimal electrochemical active surface area (EASA) of the modified electrode is obtained to be 1.67 cm2 for 20 cycles which are higher than that of the previously reported Au nanoparticles based literature. The developed material was used as an electrode modifier for the detection of hydrazine. As expected, the amperometric hydrazine sensor shows a very low detection limit of 8 nM with a high sensitivity of 7.5 µA µM−1 cm−2. The excellent analytical parameters of the F-CNF@Au/GCE modified electrode over the various related modified electrodes suggest that the electrode can be useful for use in trace level detection of hydrazine in several industrial and pharmaceutical applications.

Intercalation of Europium Inclusion Complex of β-Cyclodextrin into Layered Double Hydroxides Through Layer-By-Layer Assembly and Its Luminescent Properties

In this work, organic–inorganic hybrid ultrathin transparent films (UTFs), produced by layer-by-layer (LBL) assembly of the europium inclusion complex of [Formula: see text]-cyclodextrin ([Formula: see text]-CD) and Mg–Al-layered double hydroxide (MgAl–NO3–LDHs) nanosheets, are reported. UV-visible (UV-Vis) absorption and fluorescence spectroscopy show orderly growth of the europium inclusion complex of [Formula: see text]-CD/layered double hydroxide (EICC/LDH) films with an increasing number of deposition cycles. X-ray diffraction and scanning electron microscopy measurements indicate that the films feature periodic layered structures with uniform surface morphology. Moreover, when EICC is assembled with inorganic rigid LDH nanosheets, the lifetimes are prolonged due to the isolation effect, and the UTFs are transparent with high brightness, which indicate that these films could serve as new optical materials.

Qualifying ultrathin alumina film prepared by plasma-enhance atomic layer deposition under low temperature operation

Preparation of ultrathin alumina (Al2O3) films through Plasma-Enhanced Atomic Layer Deposition (PE-ALD) at low substrate temperature is discussed. The present work aims to investigate the physical mechanism of the PE-ALD deposition process and also the characteristics of the ultrathin alumina films on silicon 〈100〉 wafer deposited using the technique. The deposition was performed using trimethyl aluminum (Al (CH3)3) as the precursor and argon gas for purging. During deposition, the target temperature was kept constant at ~80, 100 and 150°C and the pressure was ~1.3×10−2Pa. Two deposition cycles were tested, 400 and 800 cycles. As for understanding the process, the films deposited with and without oxygen plasma were compared. Various thin film characterization techniques, including Atomic Force Microscope (AFM), ellipsometry, Raman spectrometry measurement, X-ray diffraction (XRD), and indentation technique, were applied for investigating the film properties. A transmission electron microscope (TEM) equipped with high-angle annular dark-field imaging line scan modes and energy-dispersive X-ray spectroscopy acquisition was used for imaging thin film cross-sections. We found that the number of deposition cycles did not affect the substrate surface roughness as evidenced by AFM images. The mechanical property, the hardness of the film deposited with 800 cycles and plasma was the best. Raman spectroscopy measurements showed that a Al-O-Si phase exists when the films were deposited at 100°C and 150°C for 400 and 800 cycles under oxygen plasma atmosphere. While no Al-O-Si phase existed after the same number of ALD deposition cycle without plasma. Results from XRD measurements indicated that the films deposited at 100°C and 150°C for 400 and 800 cycles under oxygen plasma atmosphere has an Al-O structure. TEM images clearly displayed the interface between the thin films, SiO2 interface layers and Si substrates. As for the sample deposited at 80°C, an Al2O3 film was hardly seen, but when increasing the deposition temperature to 100°C and 150°, films started to build on top of the substrate. However, for all deposition conditions, TEM revealed that the amounts of carbon atoms in the reaction site remained relatively high.

(Invited) Impact of the Metal Gate on the Oxide Stack Quality Assessed by Low-Frequency Noise

It is well-established that the gate oxide quality and reliability strongly depend on the type of high-k and interfacial oxide layer, the deposition method and the implementation of possible post-deposition heat or passivation treatments. As a result, the low-frequency noise magnitude may be largely affected by the gate stack processing details [1]. What is less studied is the impact of the gate material itself on the gate stack quality. Early assessments already indicated an impact of the number of TiN Atomic Layer Deposition (ALD) cycles on the noise Power Spectral Density (PSD) [2]. It is the aim of the present work to review the low-frequency noise of High-k/Metal Gate (HKMG) MOS transistors with emphasis on the role of the specific gate metal. Devices with different architectures (planar, FinFET and NanoWire (NW) FETs) will be considered in addition to the gate first versus gate last integration [3.4] As a first example, the impact of the W plug processing on the LF noise for planar pMOSFETs is shown in Fig. 1. The current noise PSD (SI) in linear operation (VDS=-0.05 V) at a frequency f=10 Hz is shown to become higher for the B2H6 precursor case, compared with the W deposition with SiH4 precursor. The higher noise is interpreted in terms of a higher oxide trap density, which is evidenced by the hump at about 100 mA drain current (ID), which is thought associated with a gate oxide trap, causing a Random Telegraph Signal (RTS). The impact on the gate stack quality (noise) of high-k Silicon-on-Insulator (SOI) and bulk FinFETs is shown in Figs 2 [5] and 3,4 [6], respectively. In the first case, the effective oxide trap density, derived from the input-referred voltage noise PSD increases with the TiN thickness, which also results in a degradation of the static characteristics, i.e., the low-field electron mobility [5]. Even for input-output (IO) devices with a rather thick thermal oxide, the gate material can play a strong role in the noise: comparing Figs 3 and 4, it is clear that both the magnitude and the slope (frequency index) of the spectra are different for a pFinFET with a standard TiN gate versus a TaN one. It will be shown that the latter devices may yield a better gate stack quality (a lower trap density) which becomes similar to that of a SiO2/polysilicon reference. Ultimately, the NW architecture will take over at the end of the Roadmap due to superior gate control of the short-channel effects. Again, it has been shown that for NWFETs the gate metal may have a strong effect on the oxide trap density, as derived from 1/f noise [7,8]. An example is given in Fig. 5, showing a clear correlation between the DC parameters (low-field mobility) and the oxide trap density (Not) derived from the 1/f noise PSD. A more detailed study of the trap density profile in Fig. 6 reveals an increase of Not towards the metal gate for the TiN device, which is absent for the TiAl case. This suggests a possible oxygen scavenging effect of Ti on the gate stack [9], creating an excess of “noisy” oxygen vacancy centers in the high-k layer.

Atomic layer deposition—A novel method for the ultrathin coating of minitablets

We introduce atomic layer deposition (ALD) as a novel method for the ultrathin coating (nanolayering) of minitablets. The effects of ALD coating on the tablet characteristics and taste masking were investigated and compared with the established coating method. Minitablets containing bitter tasting denatonium benzoate were coated by ALD using three different TiO2 nanolayer thicknesses (number of deposition cycles). The established coating of minitablets was performed in a laboratory-scale fluidized-bed apparatus using four concentration levels of aqueous Eudragit® E coating polymer. The coated minitablets were studied with respect to the surface morphology, taste masking capacity, in vitro disintegration and dissolution, mechanical properties, and uniformity of content. The ALD thin coating resulted in minimal increase in the dimensions and weight of minitablets in comparison to original tablet cores. Surprisingly, ALD coating with TiO2 nanolayers decreased the mechanical strength, and accelerated the in vitro disintegration of minitablets. Unlike previous studies, the studied levels of TiO2 nanolayers on tablets were also inadequate for effective taste masking. In summary, ALD permits a simple and rapid method for the ultrathin coating (nanolayering) of minitablets, and provides nanoscale-range TiO2 coatings on porous minitablets. More research, however, is needed to clarify its potential in tablet taste masking applications.

Optimization of the Photoanode of CdS Quantum Dot-Sensitized Solar Cells Using Light-Scattering TiO2 Hollow Spheres

CdS quantum dot-sensitized solar cells (QDSCs) have been fabricated and their photoanode optimized by altering the thickness of the photoelectrode and CdS deposition conditions and applying a ZnS electron-blocking layer and TiO2 hollow spheres. Hydrothermally grown TiO2 nanocrystals (NCs) with dominant size of 20 nm were deposited as a sublayer in the photoanode with thickness in the range from 5 μm to 10 μm using a successive ionic layer adsorption and reaction (SILAR) method. The number of deposition cycles was altered over a wide range to obtain optimized sensitization. Photoanode thickness and number of CdS sensitization cycles around the optimum values were selected and used for ZnS deposition. ZnS overlayers were also deposited on the surface of the photoanodes using different numbers of cycles of the SILAR process. The best QDSC with the optimized photoelectrode demonstrated a 153% increase in efficiency compared with a similar cell with ZnS-free photoanode. Such bilayer photoelectrodes were also fabricated with different thicknesses of TiO2 sublayers and one overlayer of TiO2 hollow spheres (HSs) with external diameter of 500 nm fabricated by liquid-phase deposition with carbon spheres as template. The optimization was performed by changing the photoanode thickness using a wide range of CdS sensitizing cycles. The maximum energy conversion efficiency was increased by about 77% compared with a similar cell with HS-free photoelectrode. The reason was considered to be the longer path length of the incident light inside the photoanode and greater light absorption. A ZnS blocking layer was overcoated on the surface of the bilayer photoanode with optimized thickness. The number of CdS sensitization cycles was also changed around the optimized value to obtain the best QDSC performance. The number of ZnS deposition cycles was also altered in a wide range for optimization of the photovoltaic performance. It was shown that the maximum efficiency was increased by about 55% compared with a similar QDSC with ZnS-free bilayer photoanode. The final improvement was carried out by applying methanol-based Cd precursor solution in the SILAR deposition process. The best photoanodes from the previous stages were selected and used in this sensitizing process. Besides, nanocrystalline TiO2 sublayers with different thicknesses were applied for further optimization. The results revealed that maximum power conversion efficiency of 3.7% was achieved as a result of such improvement, for a QDSC with optimized double-layer photoanode including TiO2 HSs and NCs and ZnS blocking layer.

Rational design of CdS@ZnO core-shell structure via atomic layer deposition for drastically enhanced photocatalytic H2 evolution with excellent photostability

Photocatalytic H2 evolution is highly attractive for converting abundant solar energy to valuable fuel. Herein, we report the use of an atomic layer deposition (ALD) technology to fabricate a new class of CdS@ZnO core-shell heterostructure. The rationally designed ultrathin ZnO shell not only allows the light to be absorbed by CdS core, but also provides an intimate heterojunction interface between ZnO shell and CdS core. The amount of ZnO shell coated on CdS core is finely tuned by the number of deposition cycles, and the obtained CdS@ZnO with 100 ALD deposition cycles displays the optimal photocatalytic H2 evolution rate of 11.36mmol/g/h. When Pt and PdS are used as the co-catalysts, the H2 evolution rates are further enhanced to 71.39 and 98.82mmol/g/h, respectively, which are 4.1 and 5.7 times higher than the highest reported value (17.40mmol/g/h) among CdS-ZnO catalyst systems. Detailed characterization reveals that the drastically enhanced photocatalytic activity can be attributed to not only efficient space separation of the photo-induced electrons and holes resulted from the formation of a direct Z-scheme photocatalytic system between crystalline ZnO and CdS, but also the intimate contact at molecular scale between the two semiconductors. Due to the coverage of ALD-prepared crystalline ZnO shell on CdS core, the CdS@ZnO core-shell structures exhibit excellent photostability.

Photovoltaic performance of an alternating cold–hot method deposited CdSe thin films

Cadmium selenide (CdSe) thin films were prepared on indium tin oxide substrate by an alternating cold–hot method, in which cadmium nitrate solution was used as a cold deposition solution, while sodium selenite and potassium borohydride mixed solution was used as a hot deposition solution. The influences of the preparation conditions such as the concentration of Cd(NO3)2, the number of deposition cycle and the cycle time, on the photoelectric performance of the sample under simulated sunlight were explored. The results show that the CdSe thin film prepared under the reaction conditions of 0.06 mol/l Cd(NO3)2 at the tenth deposition cycle (30 s per cycle) reaches the highest photovoltage of 0.285 V. Under the simulated solar illumination, the open-circuit voltage and short-circuit currents are 0.419 V and 5.57 mA/cm2, respectively. X-ray diffraction indicates that the strongest diffraction peak at 42.215° of the (111) crystal plane is corresponding to 15.15 nm CdSe nanocrystals. Scanning electron microscopy observation shows that the thickness of the CdSe film is about 200 nm and the size of the spherical and uniformly dispersed nanocrystals is around 50 nm.

Low band‐gap CuIn(S,Se)2 thin film solar cells using molecular ink with 9.5% efficiency (Phys. Status Solidi C 6/2017)

In order to achieve low band-gap thin film solar cells which can play an important role in tandem solar cells combined with perovskite top solar cells, the preparation of chalcopyrite absorbers is a major task. Wang et al. (article no. 1600169) report a non-vacuum simple solution coating approach for CuIn(S,Se)2 absorbers using an air stable molecular ink containing metal chlorides and thiourea in organic solvents. Careful balancing of ink concentration, number of precursor deposition cycles, and annealing temperature profile will transform the multilayer precursor into a sufficiently thick, continuous, large grained film as required for high quantum efficiency, and good red response of the cells. These optimizations aimed at high photo current have already led to an efficiency of 9.5% at a band-gap of 1.02 eV.

Growth mode of alumina atomic layer deposition on nanopowders

Alumina films were grown by atomic layer deposition in a rotary reactor on tungsten nanopowder with an average particle size of 54 nm. Films of various thicknesses were formed using trimethylaluminum and water at a reaction temperature of 110 °C by varying the number of deposition cycles from 2 to 78. The sharp contrast between the deposited alumina shell and the tungsten core in transmission electron microscopy allows for easy film thickness measurements and determination of the film thickness as a function of the deposition cycle. The growth curve shows that the rate of film thickness increase does not follow a single linear response but instead consists of three characteristically different growth phases. These phases occur in different deposition cycle regimes: phase I occurs in ≤5 cycles, phase II between 5 and ∼15 cycles, and phase III begins in ∼15 cycles and continues until at least 78 cycles. The average growth per cycle for phases I, II, and III is ∼4.5, <1, and 2 Å/cycle, respectively. The average growth per cycle for phase III is in excellent agreement with literature values for alumina growth on nanopowder and corresponds to ∼1 monolayer per cycle. The distinctly high/low average growth per cycle in phase I/phase II can be explained by the preferential contribution of added alumina in perpendicular/lateral growth of islands. Films grown from two deposition cycles include tall islands and regions which are ≤2 monolayer thick, similar to the dimpled surface of a golf ball. The amount of ≤2 monolayer thick regions decreases in areal density with an increase in the number of deposition cycles, resulting in an almost plateau followed by a linear increase in the growth curve and suggesting a transition of the growth mode. Such evolutions in growth are best described as the Stranski–Krastanov and Frank Vander Merwe type.

Enhanced Kinetics of Electrochemical Hydrogen Uptake and Release by Palladium Powders Modified by Electrochemical Atomic Layer Deposition.

Electrochemical atomic layer deposition (E-ALD) is a method for the formation of nanofilms of materials, one atomic layer at a time. It uses the galvanic exchange of a less noble metal, deposited using underpotential deposition (UPD), to produce an atomic layer of a more noble element by reduction of its ions. This process is referred to as surface limited redox replacement and can be repeated in a cycle to grow thicker deposits. It was previously performed on nanoparticles and planar substrates. In the present report, E-ALD is applied for coating a submicron-sized powder substrate, making use of a new flow cell design. E-ALD is used to coat a Pd powder substrate with different thicknesses of Rh by exchanging it for Cu UPD. Cyclic voltammetry and X-ray photoelectron spectroscopy indicate an increasing Rh coverage with increasing numbers of deposition cycles performed, in a manner consistent with the atomic layer deposition (ALD) mechanism. Cyclic voltammetry also indicated increased kinetics of H sorption and desorption in and out of the Pd powder with Rh present, relative to unmodified Pd.