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The comprehension of the solid–liquid interface associated with the poor charge carrier dynamic of hematite has prevented its commercial application as a photoanode in a photoelectrochemical cell. ...

A micromachined thin film thermocouple (TFTC), that is, a contact-type temperature sensor, was fabricated to diagnose the physiological state. The TFTC involved two metal films (copper and constantan) with considerably different Seebeck coefficients. Six types of TFTCs with different film thickness values were fabricated and experimentally characterized to determine the thickness-dependent temperature coefficient attesting to a high sensitivity of the sensors. The performance of each TFTC was evaluated by measuring the induced thermal electric motive force and temperature in the temporal and spatial domains by using a data acquisition board and an infrared camera, respectively. Moreover, an in vivo experiment of the proposed TFTC with the highest temperature coefficient (38.9 µV/°C) was conducted by measuring the body temperature difference of an anesthetized porcine model during its euthanasia process to evaluate the device performance.

Thin films of poly (3-hexylthiophene), abbreviated as P3HT, are widely used systems of semiconducting polymer for applications in organic electronic devices. We studied the microstructure of spin-c...

Tellurene, probably one of the most promising two-dimensional (2D) system in the thermoelectric materials, displays ultra-low thermal conductivity. However, a linear thickness-dependent thermal conductivity of unique tellurium nanoribbons in this study reveals that unprecedently low thermal conductivity can be achieved via well-defined nanostructures of low-dimensional tellurium instead of pursuing dimension-reduced 2D tellurene. For thinnest tellurium nanoribbon with thickness of 144 nm, the thermal conductivity is only ∼1.88 ± 0.22 W·m−1·K−1 at room temperature. It’s a dramatic decrease (45%), compared with the well-annealed high-purity bulk tellurium. To be more specific, an expected thermal conductivity of tellurium nanoribbons is even lower than that of 2D tellurene, as a result of strong phonon-surface scattering. We have faith in low-dimensional tellurium in which the thermoelectric performance could realize further breakthrough.

Ultrascaled WS2 field-effect transistors (FETs) fabricated on exfoliated multilayer channels with excellent ON-state and OFF-state performance are reported. Recorded high ON-state current ( ${I}_{ \mathrm{\scriptscriptstyle ON}}$ ) and ultralow contact resistance ( ${R}_{C}$ ) were achieved in a double-gated FET at a scaled overdrive voltage ( ${V}_{OV}\boldsymbol = {V}_{GS}\boldsymbol -{V}_{TH}$ ), reaching >600 ( $\boldsymbol \mu \text{A}/\boldsymbol \mu \text{m}$ ) normalized to footprint at ${V}_{DS}\boldsymbol =1$ V and ${V}_{OV}\boldsymbol =2$ V with a ${R}_{C}~\sim ~500$ ( $\Omega \times \mu \text{m}$ ). We report statistics of more than 50 FETs with varying channel lengths, showing excellent OFF-state behavior with small threshold voltage ( ${V}_{TH}$ ) variations, near-ideal subthreshold slope (SS), and small drain-induced barrier lowering (DIBL). Various channel thicknesses ( ${T}_{CH}$ ) ranging from 2.1 to 7 nm were carefully evaluated in terms of short channel effects (SCEs) and ON-state current, and a WS2 body thickness of 2.1 nm (three layers, the thinnest in our statistics) shows the best performance in both ON-state and OFF-state.

The dielectric constant (e) is a key parameter to consider when determining the fundamental electrical properties of the charging and screening of charges in optoelectronic devices based on two-dim...

Ruddlesden-Popper perovskites possess a rich variety of multiple phases due to their mixed organic cations and variable layer numbers. However, the direct observation of these phases and their optical performance in ultrathin nanosheets, have rarely been reported. Here we demonstrate, through a one-pot CVD synthesis method to incorporate MA(+) and NMA(+) cations into PbI2 simultaneously, that the stackings of Ruddlesden-Popper phases with a distribution of a number of layers n can be produced within a single perovskite nanosheet. As featured by the micro-, time-resolved and temperature-dependent photoluminescence measurements, the optical properties are highly dependent on the nanosheet thickness. The work was financially supported by the National Key R&D Program of China (Grant No. 2020YFA0308900), the National Natural Science Foundation of China (Grant No. 92064010, 61801210, 91833302), the Natural Science Foundation of Jiangsu Province (Grant No. BK20180686), the China postdoctoral Science Foundation (2020M683555), the funding for "Distinguished professors" and "High-level talents in six industries" of Jiangsu Province (Grant No. XYDXX-021), the Fundamental Research Funds for the Central Universities, the Key Research and Development Program of Shaanxi Province (2020GXLH-Z-020, 2020GXLH-Z-027) and the start-up foundation of Northwestern Polytechnical University and Nanjing Tech University.

Using ab initio molecular dynamics, we show that a recently discovered form of 2D Ga—gallenene—exhibits highly variable thickness dependent properties. Here, 2D Ga of four, five and six atomic layers thick are found to be thermally stable to 457 K, 350 K and 433 K, respectively; all well above that of bulk Ga. Analysis of the liquid structure of 2D Ga shows a thickness dependent ordering both parallel and perpendicular to the Ga/vacuum interface. Furthermore, ground state optimisations of 2D Ga to 12 atomic layers thick shows a return to a bulk-like bonding structure at 10 atoms thick, therefore we anticipate that up to this thickness 2D Ga structures will each exhibit novel properties as discrete 2D materials. Gallenene has exciting potential applications in plasmonics, sensors and electrical contacts however, for the potential of 2D Ga to be fully realised an in depth understanding of its thickness dependent properties is required.

We experimentally determine the elastic properties of 2D HfS2 and HfSe2 – two emerging nano-materials whose moderate energy bandgap and dielectric oxidized layer make them highly attractive for functional electronic and optoelectronic systems. We found that the average Young's moduli of HfS2 and HfSe2 nano-drumheads are relatively low (45.3 ± 3.7 GPa for a 12.2 nm thick HfS2 and 39.3 ± 8.9 GPa for a 13.4 nm thick HfSe2) and depend on the thickness of the nano-drumhead (increasing with thickness for HfS2 and decreasing for HfSe2). Moreover, both materials demonstrate outstanding stretchability (fracture strength and maximal strain of 5.7 ± 0.4 GPa and 12.2–14.3%, respectively, for HfS2; fracture strength and maximal strain of 4.5 ± 1.4 GPa and 14.0–20.9%, respectively, for HfSe2), which far exceeds the stretchability of other 2D materials and of polymers that are commonly used in flexible electronic applications. Finally, we describe the controlled oxidation of HfSe2 using a relatively simple laser treatment, which increased the Young's moduli of the thin oxidized layers to 182.6 ± 54.3 GPa. The extraordinary elastic properties of HfS2 and HfSe2, together with their excellent electrical and optoelectrical properties, make these 2D materials highly attractive for use in strain engineering and in various stretchable electronic and optoelectronic applications, such as wearable devices.

We performed molecular dynamics simulations to study the effect of the layer thickness on the shear localization in Cu/Nb metallic nanolayered composites (MNCs). Our simulation results achieve good agreement with experimental results that the inverse size effect in the strength occurs in samples with layer thickness below 2.0 nm. The strain softening observed in those samples was triggered by the shear localization. The quantitative analysis revealed that the unsymmetrical dislocation transmission across the interface induces the shear localization and promotes the shear band formation in Cu/Nb MNCs. The plastic strain mainly comes from the interface sliding within the shear band.

The thickness dependent chain mobility in polymer films influenced by the interfacial effect was investigated by the cold crystallization behavior of thin poly(ethylene terephthalate) (PET) films c...

Insulator-metal transition (IMT) in a metastable phase of ZnSb-based films has been explored systematically. It is found that the reduction of thickness contributes to the precipitation of metastable structure and induces a wide controllable temperature span for the presence of metastable ZnSb phase, resulting in thickness dependent IMT of p-type ZnSb film during annealing process. The metastable structure can be obtained without any void generation after erbium-filling by the formation of crystalline/crystalline dual-phase nanostructure, which can improve the electrical transport and trigger IMT behavior with the temperature of 430 °C, providing a strategy for realizing multi-level data storage.

We report a direct observation of the thickness-dependent dielectric response of MoS2 and WSe2 via mobile charge carrier measurements based on second-harmonic electrostatic force microscopy (EFM). ...

1T phase of transition metal dichalcogenides (TMDCs) formed by group 10 transition metals (e.g. Pt, Pd) have attracted increasing interests due to their novel properties and potential device applications. Synthesis of large scale thin films with controlled phase is critical especially considering that these materials have relatively strong interlayer interaction and are difficult to exfoliate. Here we report the growth of centimeter-scale PtTe, 1T-PtTe2 and 1T-PtSe2 films via direct deposition of Pt metals followed by tellurization or selenization. We find that by controlling the Te flux, a hitherto-unexplored PtTe phase can also be obtained, which can be further tuned into PtTe2 by high temperature annealing under Te flux. These films with different thickness can be grown on a wide range of substrates, including NaCl which can be further dissolved to obtain free-standing PtTe2 or PtSe2 films. Moreover, a systematic thickness dependent resistivity and Hall conductivity measurements show that distinguished from the semiconducting PtSe2 with hole carriers, PtTe2 and PtTe films are metallic. Our work opens new opportunities for investigating the physical properties and potential applications of group 10 TMDC films and the new monochalcogenide PtTe film.

The thickness dependence of the chemical and physical properties is one fundamental characteristic shared by many two-dimensional layered transition-metal dichalcogenides, including molybdenum disu...

Effect of film thickness on the magnetic properties of inverse spinel (Fe3+)[Fe3+Fe2+]O42− has been studied using Monte Carlo simulation. The critical temperature has been obtained for different fi...

Core/shell structured ZnSe/CdSe NCs have been synthesized in this work. It shows that for a given 2.79±0.28 nm core the carrier localization regime of the ZnSe/CdSe NCs can be tuned from type-I, to...

The thickness dependence of mechanical properties of nacre in Cristaria plicata shell was studied under three-point bending tests. The results show that the mechanical behavior of nacre exhibits a strong thickness dependence. The bending strength firstly increases with the increase of specimen thickness and then becomes roughly constant as the thickness reaches a certain value of ∼2.5 mm. However, the mean value of work per unit volume increases constantly with increasing specimen thickness; meanwhile, the cracking mode changes from penetration into the platelets to deflection along the interfaces. The theoretical analyses indicate that the thickness-dependent mechanical properties of nacre are mainly caused by the variation in the number of inter-lamellar interfaces. The more the number of inter-lamellar interfaces is, the higher the strength and work of fracture of nacre under bending tests will be. However, as the number of inter-lamellar interfaces reaches a certain value (e.g., in the present specimen with 2.5 mm thickness), the strength tends to remain constant, while the work of fracture still increases. Therefore, the present research findings are expected to provide a valuable guidance for the interfacial design of nacre-like materials with high strength and toughness.

Various studies suggest that the performances of TMDs are largely thickness dependent. In this paper, we develop a chemical vapor deposition method to synthesis monolayer and bilayer MoS2 flakes with a solution precursor. The MoS2 phototransistors were prepared to investigate their optoelectronic performance. The MoS2 photodetectors exhibit high detectivity of 2.44 × 1011 and a fast response/recovery time of 97 ms/291 ms. The photoresponsivity of bilayer MoS2 flakes was found up to 7160 A W−1. Our research will pave a pathway to control the layer numbers of other TMDs nanostructures, expand the application of high performance 2D materials.

Li7La3Zr2O12 (LLZO)-based ceramics are well-known as the most promising solid electrolytes for all-solid-state lithium metal batteries. However, its practical application has been significantly hin...

There is a growing need for thicker electrode designs to achieve high energy/power for ever-increasing power needs by electronic devices and electric automobiles. Though great efforts, such as stru...

We report a remarkable thickness-dependent wrinkling behavior of oxygen plasma-treated polydimethylsiloxane (PDMS) films, in which an energy barrier separates the wrinkling mechanics into two regimes. For thick films, the film wrinkles with a constant periodicity which can be precisely predicted by the classic nonlinear finite mechanics. Reducing the film thickness below 1 mm leads to nonuniform wrinkles with an increasing periodicity which gives rise to random scattering and transparency changes under mechanical strains. By tuning the film thickness, we were able to control both the quality and size of the periodic wrinkles and further design mechanochromic devices featuring brilliant structural colors and programmable colorimetric responses. This work sheds light on the fundamental understanding of the wrinkling mechanics of bilayer systems and their intriguing mechanochromic applications.

The Co1.1Fe1.9O4 ferrite with high magnetic anisotropy has great potential to be applied in sensors, transformers, and magnetic recording, etc. However, there are few researches about improving the magnetic anisotropy of Co1.1Fe1.9O4 ferrite. In this work, the tape-casting method was adopted to fabricate laminated Co1.1Fe1.9O4 ceramics. Their relative densities are all higher than 95%, and their magnetic anisotropies especially for Δ M r (the percentage residual magnetization between in-plane and out-of-plane) and Δ H C are considerably enhanced by this method comparing with that of the Co1.1Fe1.9O4 ceramic prepared by traditional solid-state reaction. It is also found that the magnetic anisotropies of these laminated Co1.1Fe1.9O4 ceramics are thickness-dependent probably due to the effect of grain size, that is, the magnetic anisotropies can be stronger when reducing the thickness of the sample. This provides a new approach to improve the magnetic anisotropy of ferrites for electronic devices applications.

In order to obtain the optimal photoelectric properties of vertical stacked MoS2/Si heterostructure solar cells, we propose a theoretical model to address the relationship among film thickness, atomic bond identities and related physical quantities in terms of bond relaxation mechanism and detailed balance principle. We find that the vertical stacked MoS2/Si can form type II band alignment, and its photoelectric conversion efficiency (PCE) enhances with increasing MoS2 thickness. Moreover, the optimal PCE in MoS2/Si can reach 24.76%, inferring that a possible design way can be achieved based on the layered transition metal dichalcogenides and silicon.

Tunable structural colors have diverse applications ranging from displays and photovoltaics to surface decoration and art. A metal–insulator–metal (MIM) cavity structure formed by thin continuous l...

Background: The electrical and optical properties of nanoparticle-based devices depend on the shape, dimension and uniformity of these particles. Methods: In this work, we fabricated ordered Au nanodots using electron beam lithography and thermal evaporation. Au nanodot diameter and circularity varied with a changed exposure dose and resist thickness. Electron beam dose ranged from 5 fC to 200 fC for single dot patterns. Commonly used PMMA thin films of thicknesses 60 nm and 100 nm coated samples were used for investigating the resist thickness dependency with varying dose exposure. Results: The analyses of patterns show that the diameter and circularity of the Au nanodots ranged from smaller to larger diameters and from lower to higher circularities with increasing dose and resist thickness. Conclusion: The distributions of the nanodot diameter began to show Gaussian behavior at larger electron doses. Besides, single circularity value became dominant up to the medium doses and then a homogeneous distribution was observed with the increasing dose.

To explore the role of dislocation slip mode playing in the size effect of mechanical behavior of metallic materials, the tensile behavior of Cu-5at.%Mn and Cu-20at.%Mn alloys with thickness (t) spanning from 0.1 to 2.0 mm is investigated. The results reveal that the yield strength σYS of Cu-5at.%Mn alloy displays an independence of thickness, whereas the ultimate tensile strength σUTS and the uniform elongation δ show an obvious size effect. The σUTS and δ first slightly decrease as t is reduced from 2.0 to 0.5 mm, but evidently drop when t is below 0.5 mm. A similar size effect is also exhibited in Cu-20at.%Mn alloy; however, the variation trend of “the smaller the weaker” in size effect can be weakened by the planar slip of dislocations occurring during the deformation of this alloy.

Colloidal quantum dots (QDs) have attracted a great amount of attention for their appealing optoelectronic properties. In this work, the CuInS2 (CIS)/ZnS core/shell QDs based on 4.3 nm cores with various layers of ZnS shell (0 to 10) were synthesized. With the sequential growth of a ZnS shell over a CIS core, the band alignment of core/shell QDs converts from a type I to quasi-type II structure. This conversion prolongs the carrier lifetime and affects the electron transfer rate (Ket) and electron transfer efficiency (ηET). A comparative study indicates that the photovoltaic performance of CIS based QDSCs can be markedly improved by optimizing the layers of ZnS shell. The highest photo conversion efficiency (PCE) of 2.07% is obtained at optimum ZnS thickness of about 1.55 nm. These results show tuning the thickness of shell to change the band alignment is an effective strategy to manipulate the carriers transportation behaviors and thus affect the PCE of CIS-based optoelectronic devices.

Based on a bandgap thermodynamic approach, the thickness-dependent bandgap of two-dimensional transition metal dichalcogenides is modeled without any adjustable parameter. An efficient expansion in bandgap upon lowering the thickness is predicted. The thickness-dependence of bandgap is believed originated from the interlayer van der Waals (vdW) interaction, while the surface effect is characterized by the difference in atomic thermal vibration between the surface and the interior. Due to the suppression role of the interlayer vdW interaction on the thermal vibration of interior chalcogen atoms, the surface effect is variable, which changes from monotonic increase for sulfides to decrease for tellurides . The role of the interlayer vdW interaction depends on the polarity of metal-chalcogen bonds. The model predictions agree with available experiment and simulation results.

In this study, we analyzed the effect of the composition and thickness of shell material on morphology, structure and optical properties of ultrathin CdSe/CdS, CdSe/CdS/ZnS and CdSe/ZnS core-shell nanoplatelets. It is shown that the growth of CdS and ZnS shells on ultrathin CdSe nanoplatelets with excitonic absorption at 463 nm leads to the formation of flat CdSe/CdS and CdSe/CdS/ZnS and folded CdSe/ZnS core-shell heterostructures, respectively. The tuning of the first excitonic transition in a range of 510–635 nm is shown by changing the composition and thickness of the shell material. Despite large lateral sizes, the CdSe/CdS and CdSe/CdS/ZnS core-shell nanoplatelets showed narrow emission bands with about 18–21 nm width. Emission width of the CdSe/ZnS heterostructures is shown to be thickness dependent and broader than that of CdSe/CdS and CdSe/CdS/ZnS heterostructures. Such control of the electronic structure of 2D core-shell nanoparticles, simply by changing the thickness and composition of the shell material may be attractive for the light-emitting device technology and lasers.

Thickness and direct band gap are two important parameters affecting the photovoltaic performance of BiFeO3 (BFO)-based thin film. In this paper, thickness effects on the microstructure and insulating properties of BFO thin film are firstly explored. The minimum leakage current density (2.18 × 10− 5 A/cm2 at 200 kV/cm) of 200 nm thin film is obtained due to a well-crystallized polycrystalline structure with high densification. On the basis, FTO/TiO2/BFO and FTO/ZnO/BFO heterostructures are proposed and successfully prepared. It turns out that with the introduction of TiO2 and ZnO acting as electron transport layer, both heterostructures possess enhanced absorption intensity and exhibit a significant red-shift, which can be ascribed to the reduced direct band gap (Eg) of 2.66 and 2.63 eV, respectively. Particularly, ZnO/BFO possess enhanced photovoltaic with relatively large Voc, Jsc, FF and η values of 1.32 V, 3.63 mA/cm2, 0.59 and 2.86, respectively. Our results demonstrate that the introduction of electron transport layer tends to be an effective way in improving the photovoltaic performance of BFO-based films.

Transition metal dichalcogenides (TMDCs) with different thickness can greatly influence the performance of photonic devices. However, how to accurately control the layers of TMDCs and realize the a...

Magnetoelectric studies on BaTi1−xSnxO3/NiFe2O4 (x = 0.07, 0.08, 0.09 and 0.10) lead-free bilayer laminated composites were investigated at 1 kHz and resonance frequencies. The pure phase formation of BaTi1−xSnxO3 and NiFe2O4 samples was confirmed by X-ray diffraction technique. The ferroelectric BaTi1−xSnxO3 layers of different compositions having large piezocoefficient were used for the ME studies. The composites displayed their maximum magnetoelectric voltage coefficient at resonance peaks related to the 1st radial mode. The thickness dependent magnetoelectric studies on composites with x = 0.08 revealed a giant magnetoelectric voltage coefficient of 24.53 V cm−1 Oe−1 at 285 kHz under bias field condition. Remarkably, a large self-biased magnetoelectric response of the order of ~ 2–5 V cm−1 Oe−1 at resonance was exhibited by the composites. The observed large and self-biased magnetoelectric response in BaTi1−xSnxO3/NiFe2O4 composites enables them to be a useful lead-free alternative for several magnetoelectric related applications.

Electrical resistivity in amorphous Mg65Zn30Ca5 thin films with thicknesses ranging from 49 nm to 1786 nm is investigated by four-probe method at 4–300 K. It is revealed that for thickness from 94 nm to 1786 nm the Ziman-Faber diffraction model can describe temperature-dependent electrical resistivity, while for 49 nm-thick film the two-level system scattering mechanism is validated below 40 K and Ziman-Faber diffraction model above 40 K. More interface fraction between the columnar structures with enhanced heterogeneity could be the possible origin of two-level system scattering in thinnest film, instead of denser atomic packing.

The formation of GaN-based heterostructures is essential for optoelectronic applications, but it is greatly limited by the traditional heteroepitaxial method due to the impact of lattice mismatch. ...

Thin film barium titanate (BaTiO3) is a promising material in the electronics and ceramics industry owing to its compelling dielectric properties. A number of works have investigated its dielectric and structural properties, but less studied are its thermal properties particularly at sub-100 nm thicknesses. Here, we measure the room-temperature thermal conductivity of ultrathin (

PURPOSE. To evaluate the precorneal tear film (PCTF) and lipid layer (TFLL) thicknesses and thinning rates in meibomian gland dysfunction (MGD) using a combined ultra-high-resolution optical coherence tomography (OCT) and thickness dependent fringe (TDF) interferometry system. METHODS. Based on the Tear Film and Ocular Surface Society (TFOS) International Workshop on Meibomian Gland Dysfunction diagnostic algorithm, the Ocular Surface Disease Index (OSDI) and meibum grade score (MGS) were used to classify subjects into four groups: Normal (OSDI

This study examined the dependence of the role and design of hetero-gate dielectric (HGD) on semiconductor film thickness in double-gate tunnel field-effect transistors (TFETs). The optimal position of the source-side dielectric heterojunction is nearly independent of the film thickness and aligned with the source-channel junction. The optimal position of the drain-side dielectric heterojunction is 7.5 nm for the films thicker than 70 nm and 9.25 nm for the films thinner than 20 nm. The on-current enhancement by the HGD engineering significantly decreases with scaling the film thickness, mostly because of the gradual disappear of the local potential well due to the increase of the double-gate coupling in scaled TFETs.