Sb Co-doping Research Articles

Constructing Enhanced Composite Solid-State Electrolytes with Sb/Nb Co-Doped LLZO and PVDF-HFP

Composite solid-state electrolytes are viewed as promising materials for solid-state lithium-ion batteries due to their combined advantages of inorganic solid-state electrolytes and solid-state polymer electrolytes. In this study, the solid electrolytes Li6.7−xLa3Zr1.7−xSb0.3NbxO12 (LLZSNO) with Sb and Nb co-doping were prepared by a high-temperature solid-phase method. Results indicate that Sb/Nb co-doping causes lattice deformation in LLZO and increases the lithium vacancy concentration and conductivity of LLZO. Then, with the co-doped LLZSNO as an inorganic filler, a composite solid electrolyte of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was prepared with a casting method. The obtained composite solid electrolyte exhibits a high ionic conductivity of 1.76 × 10−4 S/cm at room temperature, a wide electrochemical stable window of 5.2 V, and a lithium-ion transfer number of 0.32. The Li|LiFePO4 coin battery with the composite solid electrolyte shows a high specific capacity of 161.2 mAh/g and a Coulombic efficiency close to 100% at 1 C. In addition, the symmetrical lithium battery Li|Li with the composite electrolyte could cycle stably for about 1500 h without failure at room temperature.

Enhanced electrical and energy storage performances of Fe, Sb co-doped BNBCTS ceramics synthesized via the solid-state combustion technique

In this study BNBCTS ceramics were co-doped with Fe and Sb to form (Bi0.5Na0.5)0.93(Ba0.945Ca0.055)0.07(Ti(0.9946-x)Sn0.0054)(Fe0.5Sb0.5)xO3 ceramics (denoted as BNBCTS-xFS) with various x content and were prepared via the solid-state combustion technique to enhance the electrical and energy storage performance. The effect of co-doping Fe and Sb on the phase formation, defect dipole, microstructure, electrical and energy storage properties of BNBCTS-xFS ceramics was studied. When x content increased from 0.0 to 0.030, the amount of the rhombohedral (R) phase decreased from 51 to 24 % while the tetragonal (T) phase increased from 49 to 76 %. The increased Fe and Sb content increased the defect dipole of singly/doubly charged oxygen-vacancies (VO∙/ VO∙∙) and caused more Ti4+ to transition to Ti3+, which caused the transition temperature of the ferroelectric phase to relaxor state (TF-R) in the ceramics to drop to below room temperature and it exhibited relaxor characteristics at room temperature. The ceramic with an x content of 0.010 had the largest grain size (3.06 μm), excellence ferroelectric properties (Pr ∼31.04 μC/cm2, Pm ∼38.98 μC/cm2 and Ec ∼18.28 kV/cm), the largest electro strain (∼0.175 %) and a large d33* of 350 pm/V. Moreover, when x = 0.020, the ergodic relaxor ceramic showed the smallest grain size (1.03 μm), the lowest remanant polarization (Pr) of 4.52 μC/cm2 and the lowest coercive field (Ec) of 8.37 kV/cm, at an electric field of 60 kV/cm. More importantly, energy storage properties at the electric breakdown strength (Eb = 120 kV/cm) of the ceramics with an x content of 0.020 exhibited a recoverable energy storage density (Wrec) of 1.81 J/cm3, a total energy storage density (Wtotal) of 2.95 J/cm3 and an efficiency (η) of 61.30%, with excellent thermal (∼25–150 °C) and frequency stability (∼1–100 Hz). This study provides new insights into the modulation of BNBCTS ceramics with Fe and Sb co-doping, which could effectively improve the electrical properties and energy storage properties of BNBCTS-xFS ceramics.

First principles study of the electronic structure of antimony (Sb) and samarium (Sm) doped tin dioxide (SnO2) based on big data analysis

Abstract To study the electronic structure of Sb and Sm co-doped SnO2 materials, a lattice model of Sb and Sm co-doped SnO2 is designed in this paper based on a big data analysis algorithm. The physical properties of the SnO2 ground state are described by the particle density function using the density generalized function theory. The interactions between the particles are all subsumed into the exchange-correlation generalized function by the Kohn-Sham equation. A big data analysis algorithm is used to construct the electron wave function to reflect the luminescence mechanism of the spectrum produced by the electron leap between energy levels, which makes the computational effort significantly reduced. The results show that the enthalpy change of Sb and Sm co-doped SnO2 in the design model of this paper is −5.59918, and the energy interval of the density of states of s orbitals is [2.36, 31.45]. It can be seen that the co-doping of Sm and Sb can increase the electron polarization ability and electron leap probability of SnO2 in the infrared band and enhance the infrared reflectivity, and the co-doped system has the highest electron-binding ability reflectivity.

The modulation of magnetism and charge carrier in magnetic topological insulator MnBi4Te7 by Pb and Sb co-doping

The intrinsic magnetic topological insulator (MTI) MnBi2Te4 family containing magnetic order and nontrivial topology are fantastic materials for studying exotic topological states, such as quantum anomalous Hall effect, but the strong antiferromagnetic (AFM) coupling hinders potential practical applications. Here, we carry out magnetic and transport measurements on (Mn(1−x)Pbx)Bi4Te7 (0 ≤ x ≤ 0.52) single crystals. As x increases from 0 to 0.45, the AFM exchange interaction is gradually weakened by the dilution of magnetic moments. When x reaches up to 0.52, the AFM coupling is completely suppressed and it turns into a ferromagnetic -like ground state. Additionally, Sb substitutions on Bi sites in this system can not only alter the charge carriers but also further influence the magnetism and bring multiple magnetic phase transitions under low temperatures. Our results demonstrate a MTI candidate with adjustable magnetic ground state and charge carriers in Pb and Sb co-doped MnBi4Te7, which provides a promising platform to study rich topological quantum phases and benefits the potential applications in the future.

Condensed point defects enhance thermoelectric performance of rare-earth Lu-doped GeTe

Heavy rare-earth element doping can effectively strengthen phonon scattering, suppress the lattice thermal conductivity, and enhance the overall thermoelectric performance of GeTe. However, the large electronegativity difference between rare-earth elements (such as La, Eu, and Gd) and Ge refrains the doping limit of rare-earth elements below 1 mol.% in GeTe. Here, compared with other rare earth elements, Lu was found to have a relatively small radius and electronegativity difference with Ge, which can induce a high doping level in GeTe. The result shows that Lu doping effectively reduces the lattice thermal conductivity from 0.77 W m−1 K−1 of GeTe to 0.35 W m−1 K−1 of Ge0.98Lu0.02Te at 673 K, and further induces a high zT value of 1.5 in Ge0.98Lu0.02Te at 673 K. Extra Sb alloying optimizes the carrier concentration from 1.02 × 1021 cm−3 of Ge0.98Lu0.02Te to 1.77 × 1020 cm−3 of Ge0.90Lu0.02Sb0.08Te, which results in a reasonable power factor of 33.82 µW cm−1 K−2 and a low electrical thermal conductivity of 0.75 W m−1 K−1 at 673 K in Ge0.90Lu0.02Sb0.08Te. Correspondingly, a peak zT of 1.75 at 673 K and an average zT of 0.92 within the temperature range of 303–723 K are obtained in Ge0.9Lu0.02Sb0.08Te. This study indicates that Lu and Sb co-doping can effectively boost the thermoelectric performance of GeTe-based thermoelectric materials.

Enhanced Oxygen Evolution Reaction Activity in Hematite Photoanodes: Effect of Sb-Li Co-Doping.

Co-doping represents a valid approach to maximize the performance of photocatalytic and photoelectrocatalytic semiconductors. Albeit theoretical predictions in hematite suggesting a bulk n-type doping and a surface p-type doping would deliver best results, hematite co-doping with coupled cations possessing low and high oxidation states has shown promising results. Herein, we report, for the first time, Sb and Li co-doping of hematite photoanodes. Particularly, this is also a seminal work for the introduction of the highly reactive Sb5+ directly into the hematite thin films. Upon co-doping, we have a synergistic effect on the current densities with a 67-fold improvement over the standard. Via a combined investigation with profuse photoelectrochemical measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman analyses, we confirm the two doping roles of Sb5+ and Li+ as the substitutional and interstitial dopant, respectively. The improvements are attributed to a higher charge carrier concentration along with a lower charge transfer resistance at the surface.

Improving upconversion luminescence intensity of BiTa7O19:Er3+/Yb3+ by polyvalent Sb co-doping.

BiTa7O19:Er3+/Yb3+/Sb phosphors were successfully synthesized by high temperature solid sintering. X-ray diffraction (XRD), fluorescence spectrometry and X-ray photoelectron spectroscopy (XPS), were used to analyze the phase structure, upconversion luminescence (UCL) features and Sb valence state, respectively. The results suggest that polyvalent Sb with Sb3+ and Sb5+ can replace the Ta5+ sites in a BiTa7O19 host to form a pure phase. Compared with BiTa7O19:0.1Er3+/0.4Yb3+, polyvalent Sb doping further improves UCL intensity by 1.2 times under 980 nm laser stimulation with a powder density of 44.59 W cm-2. This is due to the adjustment of the local lattice structure of BiTa7O19 by the polyvalent Sb. The maximum absolute sensitivity (SA) and relative sensitivity (SR) can be estimated from the UCL variable-temperature spectra as 0.0098 K-1 at 356 K and 0.0078 K-1 at 303 K using the luminescence intensity ratio (LIR) approach. The outcomes show that host local lattice adjustment using polyvalent elements is an effective way to improve luminescence intensity, and it is possible to use BiTa7O19:Er3+/Yb3+/Sb as a temperature sensor.

Transition from paramagnetism to ferromagnetism through additional hole doping of non-magnetic antimony in iron doped tellurium alloy

We have found an enhancement in the magnetic ordering of tellurium as a result of doping it with iron along with an additional doping of a non-magnetic element antimony. A weak ferromagnetism is observed from the magnetization hysteresis which can pave the way for new kinds of magnetic semiconductors. Using the modified solid state approach, we synthesized bulk alloys of Fe-doped tellurium with co-doping of Sb having general form Fe0.05(Te)1−xSbx; x = 0 and 0.03 and analyzed the sample for their structural, electrical and magnetic properties. Electrical resistivity measurements with varying external magnetic field has been carried out and it shows semiconducting nature for both samples. The conduction mechanism in the high temperature region follows small polaron hopping (SPH) model whereas in the low temperature region, variable range hopping (VRH) model is found to fit the data. Traditionally, though tellurium is diamagnetic in nature, x = 0 sample presents itself as a paramagnetic material as evident from the magnetization measurements. On the other hand, x = 0.03 sample has a small hysteresis which is brought about by the substitution of Sb. A negative to positive crossover is observed in the magnetoresistance plot of both samples which can be co-related to transition from variable range hopping mechanism to thermally activated hopping mechanism.

Enhancing thermoelectric properties in TiNiSi structure-type semimetal ZrNiSi by doping

The orthorhombic TiNiSi structure-type compounds show interesting electronic structures comprising in most cases a pseudogap in the density of states and several small electron and hole pockets at the Fermi energy. These features are promising and can be exploited to test their potential as thermoelectric materials for waste heat conversion. Here, we investigate the effect of electron doping in the semimetallic member $\mathrm{ZrNiSi}$ of this family. We show that by doping with Sb for Si in $\mathrm{ZrNiSi}, S$ and $\ensuremath{\sigma}$ can both be increased simultaneously for initial Sb doping defying the oppositely directed trend commonly observed in most materials. In the doped samples, $\ensuremath{\sigma}$ at $300\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ increases from $1000\phantom{\rule{0.28em}{0ex}}\mathrm{S}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ to as high as $2500\phantom{\rule{0.28em}{0ex}}\mathrm{S}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$; at the same time, the peak value of $S$, which is $\ensuremath{-}20\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{V}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ in $\mathrm{ZrNiSi}$, increases by more than a factor of two. The simultaneous enhancement of $\ensuremath{\sigma}$ and $S$ has been explained using the first-principles density functional theory based band structure calculations. The as-cast (i.e., unannealed) ${\mathrm{ZrNiSi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$ samples show phase segregation due to a spinodal-type decomposition with two coexisting TiNiSi structure-type phases with different Sb/Si ratios. The thermal conductivity ($\ensuremath{\kappa}$) in the doped samples drops significantly from $12\phantom{\rule{0.28em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ ($x=0$) to nearly $2\phantom{\rule{0.28em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ ($x=0.2$) at 300 K. As a result, the peak thermoelectric figure of merit ($zT$) increases from 0.005 $(x=0)$ to 0.023 $(x=0.2)$. Further enhancement in $zT$ is obtained by codoping of Hf (Zr site) and Sb (Si site), which improves the phase stability and chemical homogeneity while keeping the thermal conductivity still very low due to Zr-Hf point mass fluctuation, resulting in a peak $zT$ value of 0.055, i.e., almost an order of magnitude higher value than for the pristine $\mathrm{ZrNiSi}$. We show that the thermoelectric properties of TiNiSi structure-type semimetals can be enhanced by aliovalent doping. This principle can be employed on other members of the TiNiSi to improve the $zT$ in this family of compounds further.

Enhanced thermoelectric performance of n-type Nb-doped PbTe by compensating resonant level and inducing atomic disorder

The inferior thermoelectric performance of n-type PbTe limits the overall conversion efficiency in PbTe-based thermoelectric devices. Here, we introduce Sb and Cu2Te into n-type Nb-doped PbTe for achieving ultra-high thermoelectric performance. The co-doping of Sb and Cu effectively optimizes carrier concentration to compensate for the resonant level in Nb-doped PbTe alloys, and consequently achieves superior electrical performance over a wide temperature range. Meanwhile, by combining extended X-ray absorption fine structure and exhaustive electron microscopy investigations, we found Nb and Sb substitutions at Pb sites induce atomic disorders, such local mass fluctuation and local strain variation, in the lattice, and Cu2Te further results in microsized segregations and nanoprecipitates, which significantly suppress lattice thermal conductivity. Eventually, a peak ZT of ∼1.32 at 823 K and a high average ZTave ∼1.01 in the range from 323 to 823 K are achieved in the Pb0·975Nb0·02Sb0·005Te-0.004Cu2Te. Based on our findings, we innovatively employ comprehensive characterization to reveal the origin of ultrahigh thermoelectric performance in n-type Nb-doped PbTe within a wide temperature range, which should be generalized to other thermoelectric materials.

RETRACTED: Improving the Structural, Optical and Photovoltaic Properties of Sb- and Bi- Co-Doped MAPbBr3 Perovskite Solar Cell

We prepared 1% Bi- and (0, 0.5%, 1% and 1.5%) Sb- co-doped MAPbBr3 films by a sol-gel spin coating technique. For the first time, the detailed structural properties including grain size, dislocation line density, d-spacing, lattice parameters, and volume of co-doped MAPbBr3 films have been investigated. XRD confirmed the cubic structure of MAPbBr3 with high crystallinity and co-doping of Bi and Sb. The 1% Bi and 1% Sb co-doping have a surprising effect in MAPbBr3 structures, such as large grain size (59.5 nm), d-space value (6.23 Å), small dislocation line dislocation (2.79 × 1018 m−2), and small lattice parameters (a = b = c = 6.3 Å) and volume of unit cell. The detailed optical properties, including energy band gap (Eg), refractive index (n), extinction coefficient (k) and dielectric constant (Ɛ), which are very important for optoelectronics applications, were investigated by UV-Vis spectroscopy. The film of 1% Bi and 1% Sb co-doped MAPbBr3 showed good optical response including small Eg, high n, low value of k, high real and low imaginary parts of dielectric constant, making it good for solar cell applications. Solar cells were fabricated from these films. The cell fabricated with pure MAPbBr3 has Jsc of 8.72 mA cm−2, FF of 0.66, Voc of 1.29 V, and η of 7.5%. All the parameters increased by co-doping of Bi and Sb in MAPbBr3 film. The cell fabricated with 1% Bi and 1% Sb co-doped MAPbBr3 film had high current density (12.12 mA-cm−2), open circuit voltage (Voc), fill factor (0.73), and high efficiency (11.6%). This efficiency was 65% larger than a pure MAPbBr3-based solar cell.

Ultralow Lattice Thermal Conductivity and Enhanced Mechanical Properties of Cu and Sb Co-Doped SnTe Thermoelectric Material with a Complex Microstructure Evolution

SnTe is an exceptionally promising eco-friendly thermoelectric material that continues to draw immense interest as a source of alternative energy recovered from waste heat energy. Here, we investigate the effect of introducing Cu as a single doping element rather than phase separated in SnTe followed by Sb co-doping to tune the lattice thermal conductivity. A microstructure evolution was observed which influences the thermoelectric performance of these SnTe-based materials. An overall power factor of ∼22 μW/cmK2 and an ultralow lattice thermal conductivity of 0.39 W/mK are reported. A maximum ZT of 0.86 is also reported with an all-time record high hardness value of 165 Hv among SnTe-based thermoelectric materials. Through DFT calculations, we show that Cu opens the band gap of SnTe, whereas Sb in the presence of Cu introduces resonance levels and causes band convergence. This kind of enhanced thermoelectric performance is paramount for the application of SnTe in recovery of heat into useful electrical energy.

Doping and Co-doping effects of Fe and Sb on the structural and optical properties of elemental Tellurium

In recent times, Tellurium in its elemental form has been studied for a variety of applications owing to its narrow band gap. Doping with impurities can bring about variations and in this respect, we have prepared bulk alloys of Fe-doped Tellurium with co-doping of Sb having a general form Fe0.05(Te)1-xSbx; x = 0 and 0.03 using the modified solid state technique. The sample is characterized for its structural and optical properties. XRD pattern displays presence of single phase hexagonal structure of Tellurium having space group P3121. X-ray line profile analysis has been carried out using Scherrer equation, Williamson-Hall method and Size-Strain plot. These approaches reveal the presence of internal lattice strain in the system which influences peak broadening. Band gap values of the bulk alloy deduced from the FTIR spectra is found to undergo drastic variations due to the doping and co-doping effects. The Raman measurements show splitting of Raman active peaks corresponding to A1 and E2 modes.

The effect of Sr and Sb co-doping on structural, morphological and thermoelectric properties of BaSnO3 perovskite material

BaSnO3 (BSO) is one of the promising perovskite materials for high temperature thermoelectric applications. The pure BSO, Sr and Sb co-doped BSO materials were prepared by the polymerization complex method and annealed at 1473 K. The X-ray diffraction patterns confirmed the cubic structure of pure BSO and Sr-Sb co-doped BSO. The addition of Sr and Sb changed the morphology of BSO from microstructures to the layered and polygonal shaped nanostructure. The valence states of each elements of the samples were confirmed by the X-ray photoelectron spectroscopy. The addition of Sb5+ atom in Sn4+ site modified the electronic band structure thereby enhanced electrical conductivity. The highest power factor of 25.3 μW/(m K2) was achieved for the SrSb5(Sr: 5 mM and Sb: 5 mM in the polymerization complex method) at 578 K. The reduced thermal conductivity and increased power factor in SrSb5 resulted in the higher figure of merit of 2.1 × 10−3 at 578 K.

Complementary effect of co-doping aliovalent elements Bi and Sb in self-compensated SnTe-based thermoelectric materials

Engineering the electronic properties of SnTe through Bi and Sb co-doping to improve the thermoelectric performance.

High Quality Factor Enabled by Multiscale Phonon Scattering for Enhancing Thermoelectrics in Low-Solubility n-Type PbTe-Cu2Te Alloys.

The fundamental challenge for enhancing the thermoelectric performance of n-type PbTe to match p-type counterparts is to eliminate the Pb vacancy and reduce the lattice thermal conductivity. The Cu atom has shown the ability to fill the cationic vacancy, triggering improved mobility. However, the relatively higher solubility of Cu2Te limits the interface density in the n-type PbTe matrix, leading to a higher lattice thermal conductivity. In particular, a quantitative relationship between the precipitate scattering and the reduction of lattice thermal conductivity in the n-type PbTe with low solubility of Cu2Te alloys still remains unclear. In this work, trivalent Sb atoms are introduced, aiming at decreasing the solubility of Cu in PbTe for improving the precipitate volumetric density and ensuring n-type degenerate conduction. Benefiting from the multiscale hierarchical microstructures by Sb and Cu codoping, the lattice thermal conductivity is considerably decreased to 0.38 W m-1 K-1. The Debye-Callaway model quantifies the contribution from point defects and nano/microscale precipitates. Moreover, the mobility increases from 228 to 948 cm2 V-1 s-1 because of the elimination of cationic vacancies. Consequently, a high quality factor is obtained, enabling a superior peak figure of merit ZT of ∼1.32 in n-type Pb0.975Sb0.025Te by alloying with only ∼1.2% Cu2Te. The present finding demonstrates the significant role of low-solubility Cu2Te in advancing thermoelectrics in n-type PbTe.

Effect of the Sb content in the SnO2 lattice and N2 percentage in a mixed sputtering gas on the N solubility in SnO2 films

Herein, the hole concentration of a SnO2 film has been increased by the co-doping of Sb and N in the SnO2 host lattice. The N-substituted O content in the SnO2 lattice was observed to depend on the N2 gas percentage in a mixed sputtering gas (comprising Ar and N2) and the Sb-substituted Sn content in the host lattice. The N-substituted O content in the SnO2 lattice increased with N2 gas concentration in the mixed sputtering gas and the Sb2O3 content in the STO (Sb2O3- doped SnO2) target. An optimal number of N-substituted O and Sb-substituted Sn contents occurred for the target with 6 % wt. Sb2O3 and the mixed sputtering gas with 75 % N2, respectively, owing to the high electrical conductivity and the best crystal quality. N-substituted O and Sb-substituted Sn contents were detected using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy, and XRD pattern measurements. The N-substituted O sites in the host lattice are large enough to cause the tetragonal rutile-to-cubic phase transformation. The film crystal quality of the cubic phase is higher than that of the rutile one. The lowest resistivity and the highest hole mobility were measured to be 1.0 × 10−2 Ω cm and 4.26 cm2 V−1 s−1, respectively, corresponding to the hole concentration of 1.24 × 1020 cm−3. The electrical property and the crystal quality of p-type Sb- and N- co-doped SnO2 films were improved compared to Sb- or N- doped SnO2 films. The deposition temperature dropped 300 °C for Sb- or N- co-doped SnO2 film instead of 550 °C for Sb-doped SnO2 film. The I–V plots of SNTO-6-y/n-Si junctions under dark and light conditions corroborated that the conductive SNTO-6-y films are p-type. The results showed that the photocurrent for SNTO-6-75 diode achieves the highest value due to the high crystal quality and the low surface roughness of SNTO-6-75 film compared to the other films. The on-off photocurrent response confirmed the stable reproducibility of the SNTO-6-75 diode. The photo-electronic effect of p-type Sb- and N- co-doped SnO2 films is promising to apply for photodetector or the other optoelectronic devices.

Enhanced temperature stability in high piezoelectric performance of (K, Na)NbO3-based lead-free ceramics trough co-doped antimony and tantalum

Although KNN-based ceramics with high electric performance have been obtained by phase engineering strategy, the temperature stability is required to be the improved in the applications. Herein, a new environment-friendly 0.96K0·4Na0·6Nb0.97-xTa0.03SbxO3-0.04(Bi0.45Sm0.05)Na0·5ZrO3 (KNNTSx-BSNZ, x = 0–0.08) ceramic system was designed, which exhibits excellent piezoelectric properties and good temperature stability. A high piezoelectric property of 510 pC/N is obtained by R-T phase engineering in the ceramics with x = 0.045. The temperature stability of electric properties is improved in the temperature range of T = 20–180 °C by Ta, Sb co-doping in KNNTSx-BSNZ ceramics with x = 0.02–0.045, benefiting from the combined effects of both the enhanced relaxor behavior and high TC. Therefore, we believe that it can broaden the application of KNN-based ceramics.

Theoretical study on the electronic structures and transport properties of Ti32-xHfxNi32Sn32-ySby half-Heusler compounds

Density functional and Boltzmann transport theories were applied to investigate the electronic structures as well as the structural and transport properties of the Ti32-xHfxNi32Sn32-ySby compounds. The results revealed that the Sb-doping and Hf-doping effectively modified the charge distributions. Both Ti32Ni32Sn32 and Ti16Hf16Ni32Sn32 exhibited narrow band-gap semiconductor behaviours, while Sb-doped TiNiSn based compounds represented n-type conductors. The calculated transport properties prove that Sb is an effective donor dopant, which promotes the improvement of the electrical conductivity with negligible effect on the Seebeck coefficient. The Ti16Hf16Ni32Sn31Sb compounds exhibit the highest power factor among the Ti32-xHfxNi32Sn32-ySby compounds owing to the co-doping of Hf and Sb.

(Invited) Differential Hall Effect Metrology (DHEM) Sub-Nm Profiling and Its Application to Dopant Activation in n-Type Ge

With silicon CMOS technology approaching its limits due to continued device scaling, many potential new channel materials have been proposed. Germanium shows considerable promise due to having higher electron and hole mobilities compared to silicon. In addition, the electron and hole mobilities are similar, making it a viable option for CMOS technology. High performance Ge PMOS has been demonstrated, but NMOS has lagged behind due to the difficulty in making low resistance contacts to n-type Ge. Contact resistance is a strong function of the carrier concentration at the semiconductor surface, and it is extremely difficult to achieve high electron activation in Ge. Point defects in Ge are known to behave as acceptor sites and reduce the overall electron activation, particularly near the surface. Minimization of these defects is essential to achieving high performance Ge NMOS. Techniques such as fluorine passivation and co-doping with Sb and P have been shown to reduce the defect density and improve dopant activation, but the impact of these methods in the near-surface regime has largely been uncharacterized. Accurate analysis of dopant activation within 5 nm of the surface is critical to understanding the effectiveness of such processes on improving contact resistance.Differential Hall Effect Metrology (DHEM) is a powerful method that provides dopant activation depth profiles at sub-nm resolution. The method employs electrochemical means of reducing the electrically active thickness of a semiconductor film and determining the sheet resistance and mobility of the thinned down layer using Van der Pauw/Hall effect type measurements. Repeating this process and using differential equations, depth profiles of mobility and carrier concentration are obtained [1].We have previously used the ALProTM tool employing the DHEM technique to study the effect of Ge co-doping with Sb and P on near-surface dopant activation [2]. In Ge with only P-doping, the active dopant concentration was ~5x1018cm-3 at the surface despite the P chemical concentration being ~1x1020cm-3, indicating that only 5% of the implanted dopants were electrically active. With co-doping of Sb and P, the active electron concentration increased to ~2x1019cm-3 with a similar P chemical concentration. Prior work has shown similar increases in activation with co-doping but did not capture the significant decrease in electron concentration by 4x within 10 nm of the surface. Here, we further study the effects of the implantation and annealing process on near-surface dopant activation in n-type Ge. Samples were prepared by growing 3 µm thick epi-Ge layers on Si substrates. Sample 1 was capped with 20 nm SiO2 and Sample 2 was capped with 20 nm Al2O3 to minimize implant damage and control implant depth. Both samples were implanted first with Sb (dose: 6x1014cm-2, energy: 65 keV) followed by P (dose: 6x1014cm-2, energy: 90 keV). Post-implant anneal was done at 500°C for 10 s in N2 to activate the dopants. ALProTM and SIMS measurements were done to characterize active dopant concentration and total chemical dopant concentration, respectively.The Al2O3 capped sample (Sample 2) showed significantly lower dopant activation than the SiO2 capped sample (Sample 1) throughout the depth of the profile (Figure 1). Active electron concentration at the surface was lower by nearly an order of magnitude, decreasing from ~2x1019cm-3 to ~2x1018cm-3. Additionally, the peak concentration decreased from 1x1020cm-3 to 5x1019cm-3 at a depth of ~30 nm in both cases. The variations in the carrier profile for the Al2O3 capped sample also indicate greater process variation. SIMS profiles show that there is significant diffusion of Al into the Ge matrix after implant and anneal. Al chemical concentration is 1x1020cm-3 at the Ge surface and steadily decays up to a depth of more than 300 nm. This indicates that there is significant damage caused during the implantation process and the activation anneal is not enough to remove these defects. Al atoms then diffuse from the Al2O3 capping layer into the highly defective Ge substrate. Al is a p-type dopant in Ge and effectively counter dopes the Sb and P implants to reduce overall electron concentration in the Al2O3 capped sample. It is important to note the high resolution DHEM technique was able to resolve this important phenomenon right near the surface of the material.