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In this study, a novel yet general strategy is proposed and demonstrated to enhance the energy storage density (ESD) of dielectric capacitors by introducing a built-in electric field in the dielectric layer, which increases the applied electric field required to polarize the dielectric. By using the top and bottom electrodes of different work functions, a built-in electric field is created in the antiferroelectric layer, which leads to an increase in the critical fields for the antiferroelectric-ferroelectric phase transition and thus the enhancement of ESD. Accordingly, the TiO 2 /ZrO 2 /TiO 2 antiferroelectric capacitor with asymmetric electrodes demonstrates an ultra-high ESD of 114.5 J cm−3, which is improved by ~21% compared to the antiferroelectric capacitor without a built-in field, along with high efficiency of 76%. The achieved ESD is record-high among the HfO 2 /ZrO 2 -based lead-free antiferroelectric thin-film capacitors. The result indicates that engineering the built-in electric field can be an effective and promising approach to increasing the ESD for electrostatic supercapacitors. [Display omitted] • A novel yet general strategy to enhance energy storage density (ESD) in dielectrics by built-in field engineering is proposed and theoretically derived. • Built-in field of opposite direction causes increase of applied electric field and thus increment of ESD. • The strategy is demonstrated on an antiferroelectric supercapacitor by asymmetric electrodes and work functions, revealing 21% improvement in ESD. • A record-high ESD of 114.5 J cm− 3 among Hf/ZrO 2 -based antiferroelectrics is achieved, along with outstanding efficiency and endurance. [ABSTRACT FROM AUTHOR]

In order to diagnose acute myocardial infraction (AMI) quickly by detection of cTnI, silicon nanowire (Si-NW) transistor is chosen to be the bio-sensor. We demonstrate Si-NW biosensors coated with different dielectric materials to detect cTnI. Based on the experimental results of 14 nm SiO2 and 28 nm SiO2, it is found that high capacitance dielectrics contribute better sensitivity than that of low capacitance dielectrics. In addition, high-k material dielectrics stacked with ultrathin SiO2 sensing membrane structures are used for Al2O3 and HfO2 because SiO2 has better compatibility with 3-Aminopropyltriethoxysilane (APTES). The results show that high-k stacked structure improve the sensitivity. Based on this work, the proposed Si-NW biosensor structure is experimentally demonstrates a good potential for future applications in cTnI detections. [ABSTRACT FROM AUTHOR]

Enhanced ferroelectric properties of nanoscale ZrO 2 thin films by an HfO 2 seed layer are demonstrated in metal-ferroelectric-semiconductor (Si) capacitors and transistors prepared with a low thermal budget of 400 °C. The seeding effect of the HfO 2 layer leads to the enhancement of crystallization into the orthorhombic phase and the increase of remnant polarization of the sub-10 nm ZrO 2 /HfO 2 bilayer structure. The ferroelectric field-effect transistor with the ZrO 2 /HfO 2 bilayer gate stack reveals a large memory window of ~1.2 V and a steep subthreshold swing below 60 mV/decade. As compared with the Hf 0.5 Zr 0.5 O 2 thin film, superior ferroelectric properties of the ZrO 2 /HfO 2 bilayer structure show great potential for ferroelectric memory devices fabricated on Si substrates. [ABSTRACT FROM AUTHOR]

In past few years, there was a great amount of research on ferroelectric Al-doped HfO 2 (HAO) thin films which suffer from the need of high annealing temperatures to achieve significant ferroelectricity. In this work, we realize pronounced remnant polarization 2 P r ~29μC/cm2 of HAO using rapid electron beam annealing (EBA) with a large area. The simulation of electron beam trajectories reveals that the effect of EBA concentrates on the region ~20 nm below the sample surface, which highly benefits the process integration where a low thermal budget is required. The energy-dispersive X-ray and high-angle annular dark-field analyses reveal the interdiffusion between Al and Hf in the HAO layer treated by EBA. The pronounced ferroelectricity of HAO can be accounted for by the lattice strain, which facilities the formation of the orthorhombic phase, due to the substitution of Al for Hf as supported by the fast Fourier transformation diffraction pattern. [ABSTRACT FROM AUTHOR]

Abstract: ZnO films were prepared by atomic layer deposition upon a SiO2 layer on a Si substrate and treated by rapid thermal annealing. The optically-pumped random lasing actions with low threshold values were observed in the ZnO films on SiO2/Si substrates. With the decrease in ZnO film thickness or the increase in post-annealing duration, the stimulated emission shifted toward the shorter wavelength and the lasing threshold increased. The results can be attributed to the inter-diffusion between ZnO and SiO2, which causes the modification of bandgap renormalization in ZnO. [Copyright &y& Elsevier]

This study demonstrates the atomic layer epitaxial growth of titanium nitride (TiN) with a record-low resistivity (8.2 × 1 0 − 8 Ω∙m) by hydrogen-manipulated chemical reaction on each monolayer. The incorporation of hydrogen plasma at a specific time during atomic layer deposition is critical to activate the epitaxial growth at only 300 °C, as evidenced by X-ray diffraction pole figure and high-resolution/scanning transmission electron microscopy. The lattice misfit is relaxed within just few monolayers away from the TiN/substrate interface. An "island plus layer" mode is proposed to explain the growth of TiN, which is intrinsically composed of twins. The low resistivity and high crystallinity of the TiN epitaxial layer manifest the significant impact of the time-manipulated hydrogen tailoring on material properties. Furthermore, the hydrogen-manipulated atomic layer epitaxy benefits from large-area uniformity, low growth temperature, and no need for high-vacuum operation, which are more advantageous over molecular beam epitaxy and so exhibit promising prospects in diverse applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, tailoring the microstructures and ferroelectric(FE)/antiferroelectric(AFE) properties of nanoscale ZrO 2 thin films is demonstrated with an intentional introduction of sub-nanometre interfacial layers. The ferroelectricity of ZrO 2 thin films is significantly enhanced by the HfO 2 interfacial layers, while the TiO 2 interfacial layers lead to a dramatic transformation of ZrO 2 from ferroelectricity into antiferroelectricity. The HfO 2 and TiO 2 interfacial layers boost the formation of the polar orthorhombic phase with (111)-texture and the non-polar tetragonal phase with (110)-texture in the FE/AFE ZrO 2 thin films, respectively, as evidenced by grazing incidence, out-of-plane, and in-plane X-ray diffraction measurements. Furthermore, the modulation of ferroelectricity and antiferroelectricity of nanoscale ZrO 2 thin films by the HfO 2 /TiO 2 interfacial layers can be achieved without high-temperature annealing, which is highly advantageous to process integration. The findings demonstrate the important role of the interfaces in the effective tuning of FE/AFE properties of nanoscale thin films. [ABSTRACT FROM AUTHOR]

Continuous, uniform, and sub-10 nm Al 2 O 3 high-K dielectrics upon two-dimensional exfoliated multilayer MoTe 2 are realized by atomic layer deposition (ALD) based on a nucleation layer (NL) prepared by the ozone-based process, interfacial AlN, and low-temperature (low- T) physical adsorption. The NLs gives rise to significant reduction of the leakage current in the sub-10 nm Al 2 O 3 high-K dielectrics as shown by conductive atomic force microscopy. For the ozone-based NL, X-ray photoelectron spectroscopy (XPS) reveals the oxidation of MoTe 2 which is detrimental to the electrical properties of MoTe 2. For the AlN NL, XPS reveals that Mo N bonds were formed without Mo O bonds and no chemical shift appeared in Te- 3d XPS spectrum, indicating the AlN NL did not result in the MoTe 2 oxidation but instead the formation of an MoN layer. For the low- T NL, the XPS spectra of MoTe 2 are the same as those of the as-exfoliated MoTe 2 flake, consistent with the absence of chemical reactions during low- T physical adsorption. The result demonstrates that the NLs prepared by the low- T physical adsorption and the interfacial AlN are effective and favorable for nucleating high-quality high-K gate dielectrics on MoTe 2 transistors. • Continuous, uniform, low-leakage, and sub-10 nm Al 2 O 3 high-K dielectrics on MoTe 2. • Oxidation of MoTe 2 occurs for the ozone-based nucleation layer (NL). • No oxidation of MoTe 2 is observed for the low- T NL and AlN NL. • Low- T NL and AlN NL are preferable for nucleation engineering on MoTe 2. [ABSTRACT FROM AUTHOR]

The in-situ atomic layer doping technique was used to precisely control the Hf incorporation into the thin TiN interlayer for tailoring the effective work function (EWF) of the Pt/Ti x Hf y N bilayer metal gate stack. An analysis of the capacitance-voltage characteristics revealed the variation of the flatband voltage with the equivalent oxide thickness of the gate oxide, giving the EWF of the Pt/Ti x Hf y N bilayer metal gate stack. Instead of the EWF (~5.7 eV) of the single-layer Pt gate electrode, the EWF of the Pt/Ti x Hf y N bilayer metal gate stacks is tunable with the range from 4.54 eV to 5.17 eV by the insertion of the thin TiN interlayer and the Hf incorporation. The result indicates that the in-situ atomic layer doping technique is an effective approach to modulating the electrical properties of metal gate in future MOS devices. [ABSTRACT FROM AUTHOR]

Large stable ferroelectricity in nanoscale undoped zirconia (ZrO 2 ) thin films prepared without post-annealing has been demonstrated for the first time. Remanent polarizations up to 12 μC cm −2 were obtained in the as-deposited ZrO 2 thin films prepared by remote plasma atomic layer deposition at 300 °C substrate temperature on the Pt electrode. Ferroelectric crystallization of the films was achieved without post-annealing, which is highly beneficial to the application of the films in non-volatile memories and ultralow-power nanoelectronics. The existence of the ferroelectric orthorhombic phase with noncentrosymmetric space group Pbc 2 1 in the as-deposited ZrO 2 thin films was confirmed by high-resolution transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The sub-5 nm Hf 0.5 Zr 0.5 O 2 (HZO) thin films have been studied for years; however, they still suffer from challenges including poor ferroelectricity, wake-up effect, and the need for high-temperature annealing. In this paper, the concept and the method of "monolayer engineering" by atomic layer deposition (ALD) are proposed and implemented, which leads to dramatic improvements in the crystallinity and ferroelectricity of the HZO thin film with a thickness of only ∼4 nm at a low annealing temperature of only 370 °C. By substituting one ZrO 2 for one HfO 2 atomic layer, a high ferroelectric remnant polarization (P r) ∼15 μC/cm2 is achieved in the HZO thin film. Moreover, the pronounced ferroelectric characteristics are demonstrated in the pristine state, indicating the nearly wake-up-free property of the HZO layer. This study manifests that the monolayer engineering by ALD enables atomic tailoring to enhance the material and physical properties of nanoscale thin films. [Display omitted] [ABSTRACT FROM AUTHOR]

In the recent decade, there is a growing interest in Hf 0.5 Zr 0.5 O 2 (HZO) thin films owing to their well-behaved ferroelectricity and high compatibility with semiconductor integrated circuit technology. The ferroelectric properties of HZO are highly pertinent to the wake-up effect, which has been reported to be associated with the monoclinic (m-), orthorhombic (o-), and tetragonal (t-) phases. However, it is very challenging to distinguish the o- and t- phases by conventional X-ray diffraction. In this study, the HZO thin films with and without the need for the wake-up process to enhance the ferroelectricity were prepared, and the precession electron diffraction (PED) phase mapping technique was utilized to identify the crystalline phases in the HZO layers. The PED characterization reveals the correlation between the phase transformation and the wake-up effect in HZO. The absence of the t-phase is responsible for the wake-up-free property in the ferroelectric HZO thin film. The wake-up-free and pronounced ferroelectricity of the nanoscale HZO thin film in this study may bring a practical impact on a variety of ferroelectric applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Large-area, low-damage, and rapid electron beam annealing (EBA) technique. • Electron irradiation in a single exposure without the need of beam scanning. • Significant enhancement of the crystal quality of nanoscale GaN thin films by EBA. • Very clear lattice fringes in the HRTEM image reveals a high-quality GaN epilayer. • Low FWHM of X-ray rocking curve and low surface roughness of the 18 nm GaN layer. This paper reports significant enhancement of the crystalline quality of nanoscale GaN thin films by a large-area and rapid electron beam annealing (EBA) technique. A low full width at half maximum of only 185 arcsec of the X-ray rocking curve indicates a high-quality GaN epilayer, which is attributed to efficient energy transfer from the large-area electron irradiation into the film in a single exposure without the need of electron beam scanning. The high crystalline quality of the GaN epilayer was also evidenced by the very clear lattice fringes in the high-resolution transmission electron microscopy image. A smooth surface with a low surface roughness of the GaN layer also reveals low damage caused by the rapid EBA treatment. The promising results demonstrate that the low-damage, large-area, and rapid EBA is an effective technique for numerous applications that require an efficient annealing process with a low thermal budget. Large-area, low-damage, and rapid electron beam annealing for the efficient recrystallization of GaN thin films is demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]

The band-edge electroluminescence at room temperature from metal-oxide-silicon tunneling diodes on (1 1 0) substrates was observed. Both the transverse acoustic and the transverse optical phonon lines are necessary to fit emission spectra. A comprehensive picture composed of localized holes, phonons and interface roughness is given to describe the radiation process. The picture can be used to explain the enhanced electroluminescence intensity, as compared to photoluminescence, and can be used to understand the substrate orientation effect on electroluminescence intensity. [Copyright &y& Elsevier]

An ~6.5 nm pure ZrO 2 thin film with a giant ferroelectric remanent polarization (P r) of ~50 μ Ccm − 2 and an effective piezoelectric coefficient (d 33) of 7−9 pm/V is reported. The film was prepared on a (111)-oriented Pt electrode using plasma-enhanced atomic layer deposition at 300 °C, followed by annealing at 400 °C, and exhibited a preferred orientation of the orthorhombic (111) planes in the in-plane direction. The P r value of ~50 μ Ccm − 2 is the largest reported to date for both perovskite and fluorite nanoscale ferroelectric thin films (< 120 nm) on a Pt electrode. Furthermore, the processing temperature of 300−400 °C is the lowest reported to date to produce a P r of ~50 μ Ccm − 2 in nanoscale ferroelectrics on a Pt electrode. The giant P r , ascribed to the preferred crystal orientation, was confirmed by the positive-up negative-down (PUND) polarization measurement with a long delay time to allow the relaxation of polarization. The effective d 33 was obtained using piezoresponse force microscopy with an interferometric displacement sensor to minimize the frequency-dependent artifacts and the effects of cantilever dynamics. The low-temperature preparation of the textured ZrO 2 ultrathin film with a giant P r is extremely advantageous for device scaling and process integration in advanced nanoelectronics. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Based on the engineering of the TiN capping layer, the tailoring of the crystalline phases and the paraelectric(PE)/antiferroelectric(AFE)/ferroelectric(FE) properties of nanoscale ZrO 2 thin films are demonstrated without any post-annealing treatment. The capping by the TiN layer leads to the conversion of ZrO 2 from the PE to the AFE electrical characteristics, while the removal of the TiN capping layer results in the AFE-to-FE phase transformation of ZrO 2. The nano-beam electron diffraction, high-resolution transmission electron microscopy and X-ray diffraction characterizations identify the presence of the AFE tetragonal and FE orthorhombic phases in ZrO 2 , and the observations reveal the emergence of the out-of-plane compressive and in-plane tensile strains in the ZrO 2 layers by the TiN capping layer as well. The results demonstrate the significant impact of the TiN capping layer effect on the crystalline phases and dielectric properties of nanoscale thin films at a low temperature, which may play an important role in the FE/AFE applications which need a low thermal budget. Unlabelled Image • The TiN capping layer induces ZrO 2 transformation from paraelectric amorphous phase to antiferroelectric tetragonal phase. • Etching TiN away results in relaxation of ZrO 2 from antiferroelectric tetragonal phase to ferroelectric orthorhombic phase. • The TiN layer can modulate the antiferroelectric and ferroelectric phases in ZrO 2 thin films without high-temperature annealing. [ABSTRACT FROM AUTHOR]

A layer-by-layer, in-situ H 2 plasma treatment in each cycle of atomic layer deposition, referred to as "atomic layer hydrogen bombardment" (ALHB), is applied to improve electrical properties of ZrO 2 high-k gate dielectrics. The H 2 plasma bombardment facilitates the adatom migration due to energy delivery to each as-deposited monolayer from the H 2 plasma. In addition, the H 2 plasma treatment contributes to the removal of precursor ligands for the release of steric hindrance. Hence the ALHB treatment leads to film densification and suppression of oxygen vacancies of ZrO 2 , as evidenced by X-ray reflectivity and X-ray photoelectron spectroscopy characterizations. As a result, ~90% decrease of gate leakage current is achieved in the ZrO 2 high-k gate dielectrics with capacitance equivalent thicknesses of ~1.3 nm and ~0.6 nm in metal-insulator-semiconductor and metal-insulator-metal capacitors, respectively. The results manifest that the ALHB treatment is a promising technique to enhance dielectric and electrical characteristics of nanoscale thin films, for further progress of advanced devices such as sensors, solar cells, memories, and nanoelectronics. Image 1 • To improve the gate dielectrics, atomic layer hydrogen bombardment (ALHB) is applied. • ALHB leads to the densification of films and the suppression of oxygen vacancies. • ~90% decrease of the leakage current is achieved in ZrO 2 MIM capacitors with a low CET ~0.6 nm. [ABSTRACT FROM AUTHOR]