Sb Donor Research Articles

Regulating the Configurational Entropy to Improve the Thermoelectric Properties of (GeTe)1-x(MnZnCdTe3)x Alloys.

In thermoelectrics, entropy engineering as an emerging paradigm-shifting strategy can simultaneously enhance the crystal symmetry, increase the solubility limit of specific elements, and reduce the lattice thermal conductivity. However, the severe lattice distortion in high-entropy materials blocks the carrier transport and hence results in an extremely low carrier mobility. Herein, the design principle for selecting alloying species is introduced as an effective strategy to compensate for the deterioration of carrier mobility in GeTe-based alloys. It demonstrates that high configurational entropy via progressive MnZnCdTe3 and Sb co-alloying can promote the rhombohedral-cubic phase transition temperature toward room temperature, which thus contributes to the enhanced density-of-states effective mass. Combined with the reduced carrier concentration via the suppressed Ge vacancies by high-entropy effect and Sb donor doping, a large Seebeck coefficient is attained. Meanwhile, the severe lattice distortions and micron-sized Zn0.6Cd0.4Te precipitations restrain the lattice thermal conductivity approaching to the theoretical minimum value. Finally, the maximum zT of Ge0.82Sb0.08Te0.90(MnZnCdTe3)0.10 reaches 1.24 at 723 K via the trade-off between the degraded carrier mobility and the improved Seebeck coefficient, as well as the depressed lattice thermal conductivity. These results provide a reference for the implementation of entropy engineering in GeTe and other thermoelectric materials.

Triple group-V donors in ZnO

Triple donors have been explored in a few semiconductor materials; however, the conventional effective mass theory treatment fails at short length scales due to the high degree of localization implied by a 3+ nuclear charge. Using density functional theory, we consider the various charge states of group-V elements substituting for the Zn sublattice in ZnO under oxygen-rich conditions. For the case of Sb and Bi substitutional impurities, the (1+/0) charge state transition is shallow and has strong similarities to a (1+/0) charge transition of the more common shallow group III donors such as Ga and Al. We compare these calculations with extensive photoluminescence (PL) measurements that now exist for the Sb-related donor bound exciton in ZnO, which is known to contain substitutional Sb on Zn sites. We present new experimental data on the magneto-PL properties of the Sb-related donor bound exciton. These data confirm the strong similarity of the (+1/0) charge state transition of this center to the common group III shallow donors in ZnO. We propose that the very low binding energy (40.2 meV) of the neutral Sb donor is due to a combination of increased screening due to the two inner donor electrons, as well as the exclusion principle, resulting in a repulsive central cell potential close to the defect core.

Triple-Pnictogen Bonding as a Tool for Supramolecular Assembly.

Supramolecular assembly utilizing simultaneous formation of three pnictogen bonds around a single antimony vertex was explored via X-ray crystallography, solution NMR, and computational chemistry. An arylethynyl (AE) ligand was designed to complement the three electrophilic regions around the Sb compound. Though solution studies reveal large binding constants for individual pyridyl units with the Sb donor, the rigidity and prearrangement of the AE acceptor proved necessary to achieve simultaneous binding of three acceptors to the Sb-centered pnictogen-bond donor. Calculations and X-ray structures suggest that negative cooperativity upon sequential binding of three acceptors to a Sb center limits the utility of triple-pnictogen bonding pyridyl acceptors. These limitations can be negated, however, when positive cooperativity is designed into a complementary acceptor ligand.

Preparation and catalytic properties of the triphenylarsine and triphenylstibine-stabilized tri-heteroleptic NHC[sbnd]Pd‒allyl complexes

A series of triphenylarsine and triphenylstibine-stabilized tri-heteroleptic NHCPd‒allyl complexes were synthesized and characterized. The solid-state structures of the complexes shown mononuclear carbene palladium complexes, in which, each palladium centre was coordinated by an N-heterocyclic carbene, the η3-coordinated allyl moiety and an As or Sb donor. Further investigation of the Pd complexes as catalysts in Sonogashira coupling reaction was carried out and the obtained complexes exhibited good reactivities for aryl bromides.

Establishing the correlation between catalytic performance and N→Sb donor-acceptor interaction: systematic assessment of azastibocine halide derivatives as water tolerant Lewis acids.

A series of organoantimony(iii) halide complexes with a tetrahydrodibenzo[c,f][1,5]azastibocine framework were synthesized and employed as water tolerant Lewis acid catalysts. The results of a systematic structure-activity relationship study demonstrated that the strength of N→Sb donor-acceptor interaction could be synergistically modulated by tuning the properties of the nitrogen substituents and halogen atoms adjacent to the central antimony atom, and consequently resulted in distinct catalytic performances towards organic reactions such as Mannich, cross-condensation, cyclization-aromatization and epoxide aminolysis reaction. The fluorinated organoantimony(iii) derivatives were found to be more active than those of the chlorinated, brominated and iodinated analogues, owing to the use of an Sb-F moiety as a hydrogen bond acceptor. By comparison, the compound 6-cyclohexyl-12-fluoro-5,6,7,12-tetrahydrodibenzo[c,f][1,5] azastibocine (1d) is found to exhibit the highest catalytic activity, together with facile reusability in scale enlarged synthesis.

Identification of the shallow donor state in Sb doped ZnO by photoluminescence excitation spectroscopy

Photoluminescence excitation (PLE) spectroscopy was used to investigate the optical properties of the recently discovered 3364.3 meV antimony-related donor bound exciton (D0X) in zinc oxide. By suitable control of the growth conditions, we achieved samples in which the Sb-related donor emission was the dominant near-bandgap luminescence feature. Resonant excitation using a tunable UV source enabled the observation of the two electron transitions of the donor bound exciton, enabling the direct determination of the binding energy of the Sb donor at 42.2±0.5 meV, the lowest value yet reported for a donor in this material. The two electron transitions exhibit an unusual blue shift with increasing temperature, which is explained in terms of thermalization of excited states of the D0X initial state. The D0X excited states were probed by PLE and follow the trends of conventional shallow group III donors such as Al, Ga, and In.

Doping and Conductivity Limitations in Sb:SnO2 Nanowires Grown by the Vapor Liquid Solid Mechanism

Sb doped SnO2 nanowires have been grown via the vapor liquid solid mechanism on fused SiO2 at 800 °C and 1 mbar under a flow of Ar and O2 by using an excess of metallic Sb in conjunction with Sn. We obtain highly crystalline Sb:SnO2 nanowires with diameters of 100 nm, lengths up to 100 μm, and a tetragonal rutile crystal structure that contains Sb donor impurities as confirmed by Raman spectroscopy. The Sb:SnO2 nanowires have a maximum carrier density of 8 × 1018 cm–3 and conductivity of 2500 S/m at 300 K determined from THz conductivity spectroscopy and the Hall effect, which are significantly higher than 3 × 1016 cm–3 and 11 S/m in undoped SnO2 nanowires. The one-dimensional electron gas charge distribution has a maximum at the core but extends all the way up to the surface as shown via the self-consistent solution of the Poisson-Schrödinger equations in contrast to the case of undoped SnO2 where the surface depletion leads to a confinement of the charge distribution to the core by taking into account the energetic position of the Fermi level with respect to the conduction band at the surface. We show that the Sb impurities are not incorporated into the SnO2 lattice through the Au particles, while higher growth temperatures between 900 to 1000 °C and/or lower growth pressures between 10–2 to 10–1 mbar do not result into the incorporation of Sb impurities in the SnO2 nanowires. This is attributed to the depletion of metallic Sb during the temperature ramp, before the onset of one-dimensional growth and/or the re-evaporation of Sb impurities arriving on the surface of the SnO2 nanowires and implies a fundamental doping limitation that is challenging to overcome especially in view of the fact the one-dimensional growth was suppressed under a significant excess of Sb.

Enhanced photoelectric performance of rutile SnO2 by charge compensation effects modulated by Sb and N

The electronic structure of Sb-N co-doped SnO2 was explored by first principles calculation. The results show that Sb (donor) and N (acceptor) introduce new energy levels in the band gap, which reduce the band gap of SnO2 obviously. Besides, the carrier separation rate of the system is improved owing to the charge compensation effect of Sb and N. Consequently, the photoelectric performance of SnO2 is improved. Based on the results of theoretical calculation, the intrinsic and different ratios of Sb-N co-doped SnO2 were prepared by hydrothermal method. And the samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and x-ray photoelectron spectroscopy (XPS). The photoelectric performance of the prepared intrinsic and Sb-N co-doped SnO2 electrodes was studied. The results prove that all samples are rutile phase with the dopants Sb and N entered into SnO2 lattice by substituting Sn and O. Besides, the 5% co-doped sample has uniform spherical shape and dispersed character. The photoelectric performance tests indicate that photoelectric performance of SnO2 is enhanced by Sb-N co-doping. The maximum photocurrent value (9 μA/cm2) and minimum electrochemical impedance is achieved at the doping ratio of 5%. Theoretical calculation and experiment results indicate that Sb-N co-doped SnO2 possesses superior photoelectric performance.

Coordination of a stibine oxide to a Lewis acidic stiborane at the upper rim of the biphenylene backbone.

Our interest in bifunctional antimony Lewis acids has led us to synthesize 1,8-bis(diphenylstibino)biphenylene (2) by reaction of 1,8-bis(trimethylstannyl)biphenylene (1) with Ph2SbCl. Oxidation of this distibine with o-chloranil, followed by work-up in air afforded a biphenylene derivative (3) featuring a triarylstibine oxide connected via an Sb[double bond, length as m-dash]O → Sb bridge to the neighbouring antimony(v) center.

Effects of antimony (Sb) on electron trapping near SiO2/4H-SiC interfaces

To investigate the mechanism by which Sb at the SiO2/SiC interface improves the channel mobility of 4H-SiC MOSFETs, 1 MHz capacitance measurements and constant capacitance deep level transient spectroscopy (CCDLTS) measurements were performed on Sb-implanted 4H-SiC MOS capacitors. The measurements reveal a significant concentration of Sb donors near the SiO2/SiC interface. Two Sb donor related CCDLTS peaks corresponding to shallow energy levels in SiC were observed close to the SiO2/SiC interface. Furthermore, CCDLTS measurements show that the same type of near-interface traps found in conventional dry oxide or NO-annealed capacitors are present in the Sb implanted samples. These are O1 traps, suggested to be carbon dimers substituted for O dimers in SiO2, and O2 traps, suggested to be interstitial Si in SiO2. However, electron trapping is reduced by a factor of ∼2 in Sb-implanted samples compared with samples with no Sb, primarily at energy levels within 0.2 eV of the SiC conduction band edge. This trap passivation effect is relatively small compared with the Sb-induced counter-doping effect on the MOSFET channel surface, which results in improved channel transport.

Optically enabled magnetic resonance study ofAs75andSb121inSi28

The electron and nuclear spins of donor impurities in enriched $^{28}\mathrm{Si}$ have great potential as long-lived qubits for a silicon-based quantum information technology. The ability to resolve the hyperfine-split neutral donor ground-state levels in the near-infrared donor bound exciton transitions of the ubiquitous phosphorus impurity in highly isotopically enriched $^{28}\mathrm{Si}$ has led to new methods of hyperpolarizing and measuring the donor electron and nuclear spins. This has resulted in optically assisted magnetic resonance methods that have permitted the measurement of remarkably long nuclear coherence times for both the neutral and ionized phosphorus donor in very lightly doped and highly enriched $^{28}\mathrm{Si}$. Other shallow donors such as arsenic, antimony, and bismuth offer the potential of larger hyperfine couplings and nuclear spins as compared to phosphorus. Here, we investigate whether donor bound exciton transitions can be used to initialize and read out the nuclear spins of arsenic and antimony in $^{28}\mathrm{Si}$. The projective readout of the electron and nuclear spins is demonstrated for both $^{75}\mathrm{As}$ and $^{121}\mathrm{Sb}$, and these optical transitions can strongly hyperpolarize the nuclear spin of $^{75}\mathrm{As}$. Only a small nuclear hyperpolarization is achieved for $^{121}\mathrm{Sb}$, likely due to the relative weakness of the no-phonon transition of the Sb donor bound exciton. Optically assisted EPR and NMR is demonstrated for $^{75}\mathrm{As}$, including Hahn echo coherence time measurements of the six NMR transitions.

Establishing the Coordination Chemistry of Antimony(V) Cations: Systematic Assessment of Ph4 Sb(OTf) and Ph3 Sb(OTf)2 as Lewis Acceptors.

The coordination chemistry of the stiboranes Ph4 Sb(OTf) (1 a, OTf = OSO2 CF3 ) and Ph3 Sb(OTf)2 (3) with Lewis bases has been investigated. The significant steric encumbrance of the Sb center in 1 a precludes interaction with most ligands, but the relatively low steric demands of 4-methylpyridine-N-oxide (OPyrMe) and OPMe3 enabled the characterization of [Ph4 Sb(OPyrMe)][OTf] (2 a) and [Ph4 Sb(OPMe3 )][OTf] (2 b), rare examples of structurally characterized complexes of stibonium acceptors. In contrast, 3 was found to engage a variety of Lewis bases, forming stable isolable complexes of the form [Ph3 Sb(donor)2 ][OTf]2 [donor=OPMe3 (6 a), OPCy3 (6 b, Cy=cyclohexyl), OPPh3 (6 c), OPyrMe (6 d)], [Ph3 Sb(dmap)2 (OTf)][OTf] (6 e, dmap=4-(dimethylamino)pyridine) and [Ph3 Sb(donor)(OTf)][OTf] [donor=1,10-phenanthroline (7 a) or 2,2'-bipy (7 b, bipy=bipyridine)]. These compounds exhibit significant structural diversity in the solid-state, and undergo ligand exchange reactions in line with their assignment as coordination complexes. Compound 3 did not form stable complexes with phosphine donors, with reactions instead leading to redox processes yielding SbPh3 and products of phosphine oxidation.

Electron spin lifetime of a single antimony donor in silicon

We present measurements of the electron spin lifetime (T1) of a single Sb donor in Si. For a magnetic field (B) oriented along the [100] Si crystal direction and low temperature (T) such that kT≪gμB, we find T1−1=KB5, where K=1.7×10−3 Hz T−5. The T1−1∝B5 dependence is expected for donor electron spin relaxation due to g-factor dependence on crystal strain. The magnitude of T1 is within a factor of two of theoretical estimates and is in close agreement with values obtained for bulk donor ensembles.

Antimony–Carbon bond activation in a Pt(II) complex: The crystal structure of [Pt(9S3)(SbPh 3)(Ph)](PF 6)·CH 3NO 2

The complex [Pt(9S3)(SbPh 3)(Ph)](PF 6) forms directly from [Pt(9S3)(SbPh 3) 2](PF 6) 2 during the room temperature crystallization of the latter in nitromethane. The crystal structure shows a five-coordinate Pt(II) center containing the tridentate thiacrown ligand, a Sb donor from the triphenylstibine ligand, and a σ-coordinating phenyl group. The phenyl group forms via Sb–C bond cleavage from one of the SbPh 3 ligands in the bis complex.

Preparation and properties of cyclic and open-chain Sb/N-donor ligands

The preparations of both open-chain and cyclic mixed-donor Sb/N ligands, MeN(CH2-2-C6H4)2SbMe (1), MeN(CH2-2-C6H4SbMe2)2 (2), CH2{CH2N(Me)CH2-2-C6H4SbMe2}2 (3) and CH2{CH2N(Me)CH2-2-C6H4}2SbMe (4), are described via reaction of chlorostibines with dilithio-reagents, and their spectroscopic properties established. Air-stable stibonium derivatives of (3) and (4) have been isolated by treatment of the compounds with excess MeI, which leads to quaternisation at the Sb atoms exclusively. A crystal structure of a bis(stibonium) derivative of (3), [CH2{CH2N(Me)CH2-2-C6H4SbMe3}2]I2, reveals hypervalency at Sb through long-range Sb...N interactions (ca. 2.87 A), giving pseudo-five-membered rings fused to the aromatic rings, and distorted trigonal bipyramidal coordination at Sb. The coordinating properties of compounds (1) to (4) have been investigated through their reactions with Cu(I), Mn(I), Mo(0) and Pt(IV) reagents, and for (1) and (4) by reaction with Fe(0), giving [Fe(CO)4(L)]. The spectroscopic data (IR, 1H, 13C{1H}, 55Mn, 63Cu, 95Mo and 195Pt NMR), mass spectrometry and microanalyses for this series of complexes confirm that coordination occurs via the Sb donor atoms in all cases, with N-coordination only present in fac-[Mn(CO)3(2)](CF3SO3). Crystal structures of [Cu(2)2]BF4, [Mo(CO)4(2)] and [PtMe3I(2)] confirm the coordination modes, showing (2) functioning as a wide-angle bidentate distibine. The structures also show the amine N-donor atoms in the complexes are involved in a hypervalent SbN interaction (ca. 3.0 A) with one of the coordinated Sb atoms in each ligand, leading to significant differences in the conformations of the carbon backbones linking the Sb and N atoms. Reaction of Na3[RhCl6].12H2O with one mol equiv. of (2), (3) or (4) leads to the bis-ligand complex [RhCl2(2)2]Cl and the 1 : 1 Rh : L complexes [RhCl2(3)]Cl and [RhCl3(4)], both of which involve coordination via the Sb and N donor atoms.

Site-Specific Force Spectroscopy and Atom Interchange Manipulation at Room Temperature

An atomic force microscope (AFM) under noncontact and nearcontact modes operated at room-temperature (RT) is used for investigations of chemical identifications and lateral atom manipulations of selected single atoms on semiconductor surfaces. Noncontact AFM image can give different contrast between intermixed two chemical species. To make clear the mechanism of chemical identification, we investigated atom selective images and site-specific frequency shifts as a function of tip-sample distance in Sb,Sn/Si(111)-(√3 × √3) surface with three different intermixed elements. Recently, using nearcontact AFM, we found a lateral atom-interchange phenomenon at RT and constructed Atom Inlay, that is, atom letters consisted of 19 Sn atoms embedded in Ge(111)-c(2× 8) substrate. Here, we clarified how to construct Atom Inlay in more detail. Further, we observed atom interchange manipulation phenomena even in In/Si(111)-(√3 × √3) and Sb/Si(111)-(7× 7) intermixed systems with not only Si but also In (acceptor element in crystal Si) or Sb (donor element in crystal Si) atoms. [DOI: 10.1380/ejssnt.2006.376]

Preparation, properties and structures of the first series of organometallic Pt(ii) and Pt(iv) complexes with stibine co-ligands

The planar Pt(II) monomers [PtMe2(L-L)] and [(PtMe2)2(L'-L')2] dimers (L-L = R2Sb(CH2)3SbR2, o-C6H4(CH2SbMe2)2; L'-L' = R2SbCH2SbR2; R = Me or Ph) are obtained in good yield via reaction of [PtMe2(SMe2)2] with L-L or L'-L' in benzene. The Pt(iv) stibines, [PtMe3(L-L)I] (L-L = R2Sb(CH2)3SbR2, o-C6H4(CH2SbMe2)2 or 2 x SbPh3, SbMePh2 or SbMe2Ph) are obtained by treatment of [PtMe3I] with L-L in chloroform. These represent the first series of stable Pt(IV) stibine complexes. All of the products have been characterised by 1H, 13C{1H}, 195Pt NMR spectroscopy, electrospray mass spectrometry and analysis. Crystal structure determinations on [PtMe3{R2Sb(CH2)3SbR2}I], [PtMe3{o-C6H4(CH2SbMe2)2}I] and [PtMe3(SbPh3)2I] confirm the distorted octahedral environment at Pt, with fac Me groups and mutually cis Sb donor atoms. The Sb-Pt-Sb angle in the seven-membered chelate ring of the o-C6H4(CH2SbMe2)2 complex is ca. 96 degrees , compared to <90 degrees in the complexes with six-membered chelates. The C1-distibines R2SbCH2SbR2 afford only the dinuclear [(PtMe3)2(mu-R2SbCH2SbR2)(mu-I)2] in which the stibine ligand and two I atoms bridge two Pt atoms giving an edge sharing bioctahedral geometry which has been confirmed by a crystal structure analysis. The Pt(II) species undergo oxidative addition with MeI to give the corresponding Pt(IV) species, while the Pt(IV) species reductively eliminate ethane upon thermolysis.

Antimony as a Donor Atom in Silver Coordination Chemistry: Synthesis, IR Spectra and Structure of the Silver(I) Cyanoximate Complexes with Triphenylstibine and Triphenylphosphine Model Compounds

Silver(I) cyanoximate complexes Ag{ONC(CN)-R} (R = COPh, {L1}; COC(CH3)3, {L2}; benzothiazol-2-yl, {L3}) with triphenylphosphine and -stibine of compositions Ag(PPh3)n{L} (n = 2, 4) and Ag(SbPh3)n{L} (n = 3 for {L1} and {L2}, n = 2 for {L3}) were synthesized by the reaction of the components in acetonitrile solution and characterized by elemental analyses and IR spectroscopy. The crystal structures of Ag(SbPh3)3{L} (L = {L1} (1), {L2} (2), Ag(SbPh3)2{L3} ∙ CH3CN (3) and Ag(PPh3)2{L1} ∙ CH3CN (4), have been determined by X-ray diffraction. For all the compounds examined the coordination environment of the silver atom has the geometry of a distorted terahedron ([AgP2NO] (4); [AgSb3N] (1), (2); [AgSb2N2] (3)). The bis adducts Ag(EPh3)n{L} adopt molecular structures, in which the organic anions are coordinated in bidentate chelate fashion via the nitroso nitrogen atom and the oxygen (nitrogen for {L3}) atom of the substituent R. In the tris-stibino complexes (Ag-Sb 2.670(4) - 2.7748(8) Å; Sb-Ag-Sb 108.87(4) - 115.00(2)°) the cyanoximates are unidentate ligands and coordinated via the nitroso nitrogen atoms (Ag-N ca. 2.35(1) Å). The different behaviour of N ,O and N,N chelating cyanoximes under the same conditions suggests, that the Sb donor triphenylstibine is able to substitute the oxygen atoms in the silver(I) coordination sphere, but not the nitrogen ones. This causes the formation of 1:3 adducts of Ag{L} with SbPh3 for N ,O donors {L1} and {L2}, and only 1:2 for N,N donor anionic {L3}.

Photodesorption and electron trapping in n-type SnO2 thin films grown by dip-coating technique

Thin films of undoped and Sb-doped (2atg%) SnO2 have been prepared by sol-gel dip-coating technique on borosilicate glasses. Variation of photoconductivity excitation with wavelength and optical absorption indicate indirect bandgap transition with energy of ≅ 3.5eV. Conductance as function of temperature indicates two levels of capture with 39 and 81 meV as activation energies, which may be related to an Sb donor and oxygen vacancy respectively. Electron trapping by these levels are practically destroyed by UV photoexcitation (305 nm) and heating in vacuum to 200° C. Gas analysis using a mass spectrometer indicates an oxygen related level, which may not be desorbed in the simpler O2 form.

Theory of defect metastabilities in III-V compounds

Up to recently the observation of a defect metastability was considered to reflect a rearrangement of a defect complex, because a point defect was believed to be structurally stable. We summarize our recent theoretical studies which show that these assumptions are incorrect and that metastability of substitutional sp defects is an intrinsic property of III-V compounds. This intrinsic metastability may be observable for some centers but not for others. We compare the behavior of three defects in GaAs: the As antisite (a model for EL2), the Si impurity (a model for DX), and the Sb donor (a stable center).