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We illustrate how the interaction between reflectivity and diffraction effects cause the asymmetry in Laue intensities around the central Bragg reflection and use simulations to show the impact of structural imperfections on the intensities of Laue oscillations. Asymmetry caused by interference of the Kiessig and Laue effects is most likely to be observed for Bragg reflections at smaller 2 I i values due to the decay of Kiessig fringe intensities as 2 I i increases. The Laue interference function predicts a symmetric distribution of satellite reflections centered on each Bragg maximum, as shown in Figure 5a (blue trace), but experimentally the intensity of the Laue oscillations is often different on either side of the Bragg reflection. [Extracted from the article]

Thin films of (Ge1–xSnx)8Sb2Te11 are prepared to study the impact of Sn‐substitution on properties relevant for application in phase‐change memory, a next‐generation electronic data storage technology. It is expected that substitution decreases the crystallization temperature, but it is not known how the maximum crystallization rate is affected. Ge8Sb2Te11 is chosen from the (GeTe)y(Sb2Te3)1–y system of phase‐change materials as a starting point due to its higher crystallization temperature as compared to the common material Ge2Sb2Te5. In situ X‐ray diffraction at 5 K min−1 heating rate is performed to determine the crystallization temperature and the resulting structure. To measure the maximum crystallization rate, femtosecond optical pulses that heat the material repetitively and monitor the resulting increase of optical reflectance are used. Glasses over the entire composition range are prepared using a melt‐quenching process. While at x = 0, 97, subsequent pulses are required for crystallization, one single pulse is enough to achieve the same effect at x = 0.5. The samples are further characterized by optical ellipsometry and calorimetry. The combined electrical and optical contrast and the ability to cycle between states with single femtosecond pulses renders Ge4Sn4Sb2Te11 promising for photonics applications. [ABSTRACT FROM AUTHOR]

While a linear growth behavior is one of the fingerprints of textbook atomic layer deposition processes, the growth often deviates from that behavior in the initial regime, i.e., the first few cycles of a process. To properly understand the growth behavior in the initial regime is particularly important for applications that rely on the exact thickness of very thin films. The determination of the thicknesses of the initial regime, however, often requires special equipment and techniques that are not always available. We propose a thickness determination method that is based on X-ray reflectivity (XRR) measurements on double layer structures, i.e., substrate/base layer/top layer. XRR is a standard thin film characterization method. Utilizing the inherent properties of fast Fourier transformation in combination with a multi-Gaussian fitting routine permits the determination of thicknesses down to t ≈ 2 nm. We evaluate the boundaries of our model, which are given by the separation and full width at half maximum of the individual Gaussians. Finally, we compare our results with data from x-ray fluorescence spectroscopy, which is a standard method for measuring ultra-thin films. [ABSTRACT FROM AUTHOR]

The mechanism of the reaction between Mn and Se is shown to depend on the composition and the thickness of Mn and Se layers. Samples were prepared by modulated elemental reactants (MER) method. The elements were evaporated using either electron beam guns or effusion cells and the total amount of each element was controlled using quartz crystal monitors. Different ratios of the elements and different total amounts of the elements per repeating unit were experimentally explored. Near a one to one ratio of Mn and Se, α‐MnSe crystallizes upon deposition. Compositions near a one to two ratio of Mn to Se proceed through an amorphous intermediate for the layer thicknesses investigated, with MnSe2 crystallizing at 150 °C. Between these compositions, the two bilayer thicknesses explored evolve differently, with films with bilayer thicknesses near 0.5 nm nucleating MnSe, whereas films with bilayer thicknesses around 1 nm nucleating a mixture of MnSe and MnSe2. Samples around 80 % Se formed a previously unreported compound with a small monoclinic unit cell with lattice parameters a = 4.942(2) Å, b = 4.32(3) Å, c = 3.779(1) Å, and β = 90.13(3)°. [ABSTRACT FROM AUTHOR]

Reducing the accelerating voltage used to pattern a high-resolution inorganic thin film electron beam resist, HafSOx dramatically decreases the dose required to pattern sub-10 nm lines. Ellipsometry measurements of dose curves created for HafSOx show a dramatic increase in sensitivity without any loss in contrast. High resolution patterning at 10 keV show no decrease in obtainable feature size, producing 9 nm wide lines with half the dose required previously and no increase in line edge roughness. Monte Carlo simulations of the incident electron beam into a 22 nm thick HafSOx film predict that even lower primary beam energies, down to 5 keV, could enable patterning of sub-20 nm features with significantly enhanced throughput. This improved film sensitivity at lower beam energies enables increased throughput without loss of patterning resolution and should be extendable to other inorganic photoresists. [ABSTRACT FROM AUTHOR]

A family of multiple-component heterostructures, ([SnSe]1+ δ) m([{Mo xNb1- x}Se2]1+ γ)1([SnSe]1+ δ) m({Nb xMo1- x}Se2)1 ( m = 0, 1, 2, 3, 4 and 0.8 ≤ x ≤ 1), was self-assembled from designed amorphous precursors, and their structure and physical properties were characterized. The compounds consist of MoSe2 and NbSe2 layers with metal centers in a trigonal-prismatic environment interleaved with systematically increasing numbers of SnSe bilayers with a distorted rock salt structure. The extent of alloying of the miscible dichalcogenide constituents decreased from about 20 % for m = 0 to less than 1 % for m = 3 and 4. The decreased alloying with increased SnSe thickness suggests the diffusion lengths of Mo and Nb during self-assembly are about a nanometer. Resistivity and Hall coefficient measurements show that the electrical transport properties are similar to those of ([SnSe]1+ δ) m(NbSe2)1 ( m = 1-8) compounds, suggesting that the NbSe2 layer dominates the conductivity and that charge transfer from SnSe reduces the carrier concentration in the NbSe2 layer. [ABSTRACT FROM AUTHOR]

The scope of this work is to review the thermoelectric properties, the microstructures, and their correlation with theoretical calculations and predictions for recent chalcogenide based materials. The main focus is put on thin multilayered Bi2Te3, Sb2Te3 films, and bulk V2VI3/IV-VI mixed systems. For all films a systematic characterization of the thermoelectric properties as well as the micro- and nanostructure was performed. The degree of crystallinity of the multilayered films varied from epitaxial systems to polycrystalline films. Other multilayered thin films revealed promising thermoelectric properties. (SnSe)1.2TiSe2 thin films with rotational disorder yielded the highest Seebeck coefficient published to date for analogous materials. For bulk V2VI3/IV-VI mixed systems insides are given into a complete 'material to module' process resulting in a high performance thermoelectric generator using (1 -x)(GeTe) x(Bi2Se0.2Te2.8) ( x = 0.038). Cyclic heating of this system with x = 0.063 resulted in a drastic change of the micro- and nanostructure observed by ex situ and in situ X-ray diffraction (XRD) and transmission electron microscopy (TEM). Consequently a degradation of ZT at 450 °C from ∼2.0 to ∼1.0 was observed, while samples with x = 0.038 showed a stable ZT of 1.5. [ABSTRACT FROM AUTHOR]

(SnSe)1.2TiSe2 was found to self-assemble from a precursor containing modulated layers of Sn-Se and Ti-Se over a surprisingly large range of layer thicknesses and compositions. The constituent lattices form an alternating layer superstructure with rotational disorder present between the layers. This compound was found to have the highest Seebeck coefficient measured for analogous TiX2 containing misfit layered compounds to date, suggesting potential for low-temperature thermoelectric applications. Electrical characterization suggests that electrons transferred from SnSe to TiSe2 are responsible for the higher carrier concentration observed relative to bulk TiSe2. The transfer of charge from one constituent to the other may provide a mechanism for doping layered dichalcogenides for various applications without negatively affecting carrier mobility. [ABSTRACT FROM AUTHOR]

A new metastable compound Cr3Sb was synthesized as thin film starting from modulated elemental reactant layers. The new compound is cubic and crystallizes in the A15 structure (Cr3Si-type). A variation of the occupancy of the Sb position (0, 0, 0) was observed leading to a Cr-rich sample with formula Cr∼6Sb. In-situ X-ray diffraction and reflectivity investigations indicate an interdiffusion of the multilayers and crystallization of the new compound below 350°C. Calculations of the crystal structure and lattice parameter agree well with the experimental results. In addition the existence of a further metastable phase, a Heusler-like alloy, is discussed and supported by DFT calculations. [ABSTRACT FROM AUTHOR]

A zinc-metal dopant-oxygen precursor exposure cycle is demonstrated as a modified deposition procedure for better distribution of Al-dopants in ZnO films by atomic layer deposition with the aim to reduce the formation of nanolaminate thin films that might form with the typically used alternating ZnO and metal oxide deposition procedure. The distribution and chemical bonding states of Al-dopants were studied with various dopant deposition intervals of Zn–Al–O precursor and Zn–O cycles at 1::4, 1::9, 1::14, and 1::19 ratios. The smallest resistivity of Al-doped ZnO film without degradation of transparency was obtained at 250 °C with 5.37×10-4 Ω cm. [ABSTRACT FROM AUTHOR]

The in-plane thermal conductivity is measured to be three times lower in misfit-layered [(PbSe)0.99]x(WSe2)x superlattice thin films than disordered-layered WSe2 because of interface scattering despite a higher cross-plane value in the former than the latter. While having little effect on the in-plane thermal conductivity, annealing the p-type [(PbSe)0.99]2(WSe2)2 films in Se increases the in-plane Seebeck coefficient and electrical conductivity because of decreased defect and hole concentrations. Increasing interface density of the annealed films by decreasing x from 4 to 2 has weak influence on the in-plane thermal conductivity but increases the Seebeck coefficient and decreases the room-temperature electrical conductivity. [ABSTRACT FROM AUTHOR]

It was recently reported that misoriented layered WSe2 and (W)x(WSe2)y films possess extremely low cross-plane thermal conductivity. Here, we report that the in-plane thermal conductivity results for WSe2 and W4(WSe2)10 films measured by using a suspended device are about 30 times higher than the cross-plane values because of the in-plane ordered and cross-plane disordered structures and about six times lower than that of compacted single-crystal WSe2 platelets. The additional W layers in the W4(WSe2)10 films were found to greatly increase the in-plane electrical conductivity relative to the WSe2 films, but reduce the in-plane lattice thermal conductivity assuming the Wiedemann-Franz law. [ABSTRACT FROM AUTHOR]

Crystallographic ordering and defects in WSe2 thin films with ultralow thermal conductivity are characterized by electron imaging and diffraction in cross-sectional geometry. The results show that the film consists of oriented, coherent crystallites that are a few nanometers in diameter. Two films of different thickness with different thermal conductivity are compared. We show that the film with a lower thermal conductivity is characterized by less coherent crystallites with a greater degree of misorientation. [ABSTRACT FROM AUTHOR]

Thin films of Ge 6 Sn 2 Sb 2 Te 11 were synthesized and compared to the well-known unsubstituted phase change material (PCM) Ge 8 Sb 2 Te 11 . In situ X-ray diffraction (XRD) and temperature dependent sheet resistance measurements evidenced a significant decrease of the phase change temperature from 144 °C for Ge 8 Sb 2 Te 11 to 112 °C for Ge 6 Sn 2 Sb 2 Te 11 . The resistance measurements also revealed an intermediate step during the phase change. Detailed in situ transmission electron microscopy (TEM) and (XRD) investigations on structural ordering phenomena suggest that this intermediate step is associated with the disorder of structural vacancies on the cationic sites stable up to 130 °C. Annealing the sample beyond 130 °C leads to a subsequent ordering of vacancies and thus to the formation of a metastable primitive trigonal phase with vacancy layers. At ∼240 °C - ∼300 °C, a transition to the stable phase is observed. For the first time, an in plane movement of bi-layer defects is observed by in situ TEM as a result of a self-ordering mechanism. These findings represent new insights into the transition process on the nanoscale and suggest that tin substituted PCMs may represent promising candidates for multi-level data storage applications. [ABSTRACT FROM AUTHOR]

Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted In2O3 and In-substituted β -Ga2O3 with different degrees of substitution. X-ray total scattering and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β -Ga2O3 phase, with a minor constituent of In2O3 with significantly larger coherence lengths. This amorphous β-Ga2O3 phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure-property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF. [ABSTRACT FROM AUTHOR]

Relative humidity during the spin-processing of thin film solution precursors is often not controlled or measured, and its effect on film thickness is generally unappreciated. Herein, we report that the relative humidity during spin-processing has a marked impact on the film thickness of amorphous metal oxide (aluminum oxide and lanthanum zirconium oxide) and hafnium oxide-sulfate (HafSOx) thin films deposited from aqueous precursors. In the humidity range studied [20-95% relative humidity (RH)], film thicknesses varied by a factor of nearly 3, and this effect is independent of the metal precursor identity. Our data suggest that film thickness depends linearly on evaporation rate (100 - RH) for all systems studied, suggesting this effect is predominantly due to the unique characteristics of water as a solvent. In situ X-ray reflectivity studies of HafSOx films deposited under different humidities reveal that, while the thickness varies significantly with humidity, the density of the as-deposited films is similar, suggesting that humidity primarily affects the relative amount of material deposited. Because reproducible film thickness is critical for many applications, our data highlight the importance of controlling humidity during spin-processing. [ABSTRACT FROM AUTHOR]

Thin films with tunable and homogeneous composition are required for many applications. We report the synthesis and characterization of a new class of compositionally homogeneous thin films that are amorphous solid solutions of Al2O3and transition metal oxides (TMO x ) including VO x , CrO x , MnO x , Fe2O3, CoO x , NiO, CuO x , and ZnO. The synthesis is enabled by the rapid decomposition of molecular transition-metal nitrates TM(NO3) x at low temperature along with precondensed oligomeric Al(OH) x (NO3)3–x cluster species, both of which can be processed from aq solution. The films are dense, ultrasmooth (R rms< 1 nm, near 0.1 nm in many cases), and atomically mixed amorphous metal-oxide alloys over a large composition range. We assess the chemical principles that favor the formation of amorphous homogeneous films over rougher phase-segregated nanocrystalline films. The synthesis is easily extended to other compositions of transition and main-group metal oxides. To demonstrate versatility, we synthesized amorphous V0.1Cr0.1Mn0.1Fe0.1Zn0.1Al0.5O x and V0.2Cr0.2Fe0.2Al0.4O x withR rms≈ 0.1 nm and uniform composition. The combination of ideal physical properties (dense, smooth, uniform) and broad composition tunability provides a platform for film synthesis that can be used to study fundamental phenomena when the effects of transition metal cation identity, solid-state concentration of d-electrons or d-states, and/or crystallinity need to be controlled. The new platform has broad potential use in controlling interfacial phenomena such as electron transfer in solar-cell contacts or surface reactivity in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

We report the low temperature synthesis of highly textured CuCr 2 Se 4 thin films using the modulated elemental reactant (MER) method. The structure of CuCr 2 Se 4 is determined for the first time in its thin film form and exhibits cell parameters that are smaller than found in bulk CuCr 2 Se 4 . X-ray diffraction and precession electron diffraction show a strong degree of crystallographic alignment of the crystallites, where the <111> axis is oriented perpendicular to the substrate surface, while being rotationally disordered within the plane. Temperature and field dependent in-plane and out-of-plane magnetization measurements show that the film is ferromagnetic with a Curie temperature of 406 K CuCr 2 Se 4 synthesized utilizing the MER method shows stronger magnetic anisotropy (effective anisotropy: 1.82 × 10 6 erg cm −3 ; shape anisotropy: 1.07 × 10 6 erg cm −3 ), with the easy axis lying out of plane, and a larger magnetic moment (6 μ B /f.u.) than bulk CuCr 2 Se 4 . [ABSTRACT FROM AUTHOR]

Synthesis and transport properties of ([PbSe] 1+ δ ) 1 ( TiSe 2 ) 1 ferecrystals made from several precursors of different compositions are reported. C -lattice parameters of crystallized compounds vary by under 0.01 Å though relative cation compositions normalized to selenium content are shown to vary by over 30%. Even with a deliberate wide-range of starting precursor compositions crystallized under kinetic conditions, the variation in electrical properties of ferecrystals is less than in similar compounds grown under equilibrium conditions. The growth process of a ferecrystal appears to push impurities of excess starting material in the precursor to the surface, until impurity density becomes too high and defects are incorporated as inclusions, replacing small domains within the layered structure. Transport properties of the many compounds formed cluster into regions, with samples deposited during the same deposition cycle showing less variation. [ABSTRACT FROM AUTHOR]

A new polytype of the misfit layer compound ([SnSe] 1.16 ) 1 (NbSe 2 ) 1 with extensive rotational disorder was prepared from designed modulated elemental reactants. This polytype, previously referred to as a ferecrystal due to the extensive rotational disorder, formed over a range of compositions and precursor thicknesses and the resulting c -axis lattice parameters ranged from 1.2210(4) to 1.2360(4) nm. These values bracket the value published for the crystalline misfit layer compound prepared at high temperature. The a - and b -axis in-plane lattice parameters of both the SnSe and NbSe 2 constituents were incommensurate, which differs from the misfit layer compound formed via high temperature reaction that has a common b -axis lattice parameter for the two constituents. The in-plane area per unit cell of the ferecrystal is 1–2% larger than the compound formed at high temperature. The ferecrystalline ([SnSe] 1.16 ) 1 (NbSe 2 ) 1 compound is 1.6 times more conductive than the misfit layer compound. Hall effect measurements indicate that the ferecrystal is a p -type metal and that the higher conductivity is a consequence of higher mobility of carriers in the ferecrystalline compound. [ABSTRACT FROM AUTHOR]

(SnSe)1.2TiSe2 was found to self-assemble from a precursor containing modulated layers of Sn-Se and Ti-Se over a surprisingly large range of layer thicknesses and compositions. The constituent lattices form an alternating layer superstructure with rotational disorder present between the layers. This compound was found to have the highest Seebeck coefficient measured for analogous TiX2 containing misfit layered compounds to date, suggesting potential for low-temperature thermoelectric applications. Electrical characterization suggests that electrons transferred from SnSe to TiSe2 are responsible for the higher carrier concentration observed relative to bulk TiSe2. The transfer of charge from one constituent to the other may provide a mechanism for doping layered dichalcogenides for various applications without negatively affecting carrier mobility. [ABSTRACT FROM AUTHOR]

Nanolaminates composed of TiO2and Al4O3(PO4)2(AlPO) thin filmshave been fabricatedfrom aqueous solution precursors. By adjusting precursor concentrationsindividual layers can be controlled to a thickness near 1 nm. Characterizationby X-ray reflectivity and transmission electron microscopy (TEM) revealsnear-atomically smooth interfaces and a high degree of regularityin the film stacks. X-ray diffraction is utilized to investigate thecrystallization behavior of TiO2layers under one-dimensionalconfinement of the glassy AlPO layers. TiO2–AlPOnanolaminates incorporated into capacitor structures exhibit low leakagecurrent densities (<10 nA/cm2at 1 MV/cm) and high breakdownfields up to 5.4 MV/cm with annealing temperatures as low as 350 °C.Tailorable dielectric constants have also been demonstrated by varyingthe relative thickness of the TiO2and AlPO films. As gatedielectrics in thin-film transistors with solution-processed amorphousindium gallium zinc oxide channels, the nanolaminates exhibit smallgate leakage, enabling ideal transistor performance with incrementalmobilities near 3 cm2/V·s. [ABSTRACT FROM AUTHOR]

Abstract: Sub-micron, nanolaminated, dielectric thin films comprised of amorphous aluminum oxide phosphate (AlPO) and hafnium oxide sulfate (HafSOx) layers were fabricated in open-air conditions from aqueous inorganic precursors by spin coating with minimal thermal processing. These nanolaminated thin film insulators display an averaging effect of effective dielectric permittivity in devices with controlled AlPO:HafSOx thickness ratios, enabling tunable dielectric properties. X-ray reflectivity measurements were used to characterize film thickness, smoothness, and uniformity. Scanning electron microscopy was used to analyze final nanolaminated devices. Electrical characterization of metal-insulator-insulator-metal capacitors revealed tunable relative dielectric constants ranging from approximately 5–10 with loss tangents less than 2% at 10 kHz in devices with approximately 300 nm total dielectric thickness. The results suggest a simple, inexpensive processing approach for fabricating devices that require insulating layers with specific dielectric properties. [Copyright &y& Elsevier]

Abstract: The nucleation and growth kinetics of binary copper–selenium compounds from co-deposited copper and selenium films as a function of annealing temperature and time was investigated. The thermally driven evolution of crystalline phases was followed using differential scanning calorimetry and X-ray diffraction. Below 60% selenium, hexagonal α-CuSe formed during the deposition and a reversible endothermic transition at ∼130°C was observed for the phase transition into hexagonal γ-CuSe. Above 60% selenium the samples are amorphous as deposited and there is competition between the formation of γ-CuSe and cubic CuSe2 as annealing temperature is increased. Slow rates of temperature increase favor the formation of CuSe2 over γ-CuSe and near 66% selenium only cubic CuSe2 forms during an exothermic event between 100°C and 110°C. It is surprising that the metastable cubic CuSe2 initially nucleates and grows rather than the thermodynamically stable orthorhombic CuSe2 polymorph. Kissinger analysis yields an activation energy for nucleation of 1.6eV for cubic CuSe2. CuSe nucleates throughout the composition region investigated. Hexagonal α-CuSe reacts with selenium to form the thermodynamically stable orthorhombic polymorph of CuSe2 as the temperature approaches the melting point of selenium. [Copyright &y& Elsevier]

Abstract: The optical and electrical characteristics of SnO2 films with 0.02at.% Pt nanoparticles were studied after annealing at various temperatures. Pt nanoparticles were synthesized by a methanol reduction method and their size was limited to 3nm on average using PVP [poly(N-vinyl-2-pyrrolidone)] as a protecting agent. The electrical conduction of the SnO2 films was enhanced by the introduction of Pt nanoparticles without degradation of optical transmittance. The resistivity and transmittance of the SnO2 films with and without Pt nanoparticles after annealing at 700°C were 2.9×10−2 Ωcm and 86.45%, and 1.5×10−1 Ωcm and 85.75%, respectively. The observed enhancement in electrical properties was attributed to an increase in carrier concentration due to the addition of Pt nanoparticles. The fact that almost no change in transmittance was observed is explained by the small quantities produced and small particle sizes of the Pt nanoparticles. Well-defined 30-μm-wide direct-patterned SnO2 films containing Pt nanoparticles were formed by photochemical metal-organic deposition using a simple process including a photosensitive starting precursor, UV exposure, and removal of the un-patterned area with solvent rinsing. [ABSTRACT FROM AUTHOR]