Growth of Atomic layer-deposited Monoclinic Molybdenum Dioxide Films Stabilized by Tin Oxide Doping for DRAM Capacitor Electrode Applications.

Dynamic random-access memory (DRAM) capacitor electrodes, exemplified by TiN, face performance limitations owing to their relatively low work functions in addition to the formation of a low-k interfacial layer caused by their insufficient chemical stability. With recent advances in device scaling, these issues have become increasingly problematic, prompting the exploration of alternative electrode materials to replace TiN. Molybdenum dioxide (MoO2) has emerged as a promising candidate for this application, outperforming TiN due to its low resistivity, high work function (>5 eV), and excellent chemical stability. Moreover, monoclinic MoO2 exhibits a distorted rutile structure, enabling the in situ growth of high-k rutile TiO2 on MoO2 at low deposition temperatures. However, MoO2 deposition poses challenges because of its metastable nature compared to the more stable molybdenum oxide (MoOx) phases, such as MoO3 and Mo4O11. In this work, we successfully fabricated Sn-doped MoOx (TMO) films by atomic layer deposition (ALD) at 300 °C. A stabilized monoclinic MoO2 phase was achieved using ALD by incorporating SnOx into MoOx on both SiO2 and TiN substrates. The ALD TMO process comprised MoOx and SnOx subcycles, and the MoOx:SnOx subcycle ratio was varied from 100:1 to 20:1. High growth rates ranging from 0.19 to 0.34 nm/cycle were achieved for ALD TMO with varying the MoOx:SnOx subcycle ratio from 20:1 to 100:0. After post-deposition annealing at 500 °C, polycrystalline TMO films were obtained with smooth surface morphology. ALD TMO exhibited excellent interface quality with ALD TiO2, possessing a negligible low-k interfacial layer. Moreover, a rutile TiO2 film with a high dielectric constant of 136 was successfully grown on a 20% Sn-TMO electrode. Overall, this study provides a strategy to stabilize metastable MoO2 films using ALD, and it demonstrates the superiority of ALD TMO as a promising DRAM capacitor electrode material.

Role of a cyclopentadienyl ligand in a heteroleptic alkoxide precursor in atomic layer deposition.

Alkoxide precursors have been highlighted for depositing carbon-free films, but their use in Atomic Layer Deposition (ALD) often exhibits a non-saturated growth. This indicates no self-limiting growth due to the chain reaction of hydrolysis or ligand decomposition caused by ß-hydride elimination. In the previous study, we demonstrated that self-limiting growth of ALD can be achieved using our newly developed precursor, hafnium cyclopentadienyl tris(N-ethoxy-2,2-dimethyl propanamido) [HfCp(edpa)3]. To elucidate the growth mechanism and the role of cyclopentadienyl (Cp) ligand in a heteroleptic alkoxide precursor, herein, we compare homoleptic and heteroleptic Hf precursors consisting of N-ethoxy-2,2-dimethyl propanamido (edpa) ligands with and without cyclopentadienyl ligand-hafnium tetrakis(N-ethoxy-2,2-dimethyl propanamido) [Hf(edpa)4] and HfCp(edpa)3. We also investigate the role of a Cp ligand in growth characteristics. By substituting an alkoxide ligand with a Cp ligand, we could modify the surface reaction during ALD, preventing undesired reactions. The last remaining edpa after Hf(edpa)4 adsorption can undergo a hydride elimination reaction, resulting in surface O-H generation. In contrast, Cp remains after the HfCp(edpa)3 adsorption. Accordingly, we observe proper ALD growth with self-limiting properties. Thus, a comparative study of different ligands of the precursors can provide critical clues to the design of alkoxide precursors for obtaining typical ALD growth with a saturation behavior.

Amidoxime-Containing Zr and Hf Atomic Layer Deposition Precursors for Metal Oxide Thin Films.

In this article, we discuss the synthesis of eight novel zirconium and hafnium complexes containing amidoxime ligands as potential precursors for atomic layer deposition (ALD). Two amidoximes, viz., (E)-N'-hydroxy-N,N-dimethylacetimidamide (mdaoH) and (Z)-N'-hydroxy-N,N-dimethylpivalimidamide (tdaoH), along with their Zr and Hf homoleptic complexes, Zr(mdao)4 (1), Hf(mdao)4 (2), Zr(tdao)4 (3), and Hf(tdao)4 (4) were prepared. We further synthesized heteroleptic compounds with different physical properties by introducing cyclopentadienyl (Cp) ligand, namely, CpZr(mdao)3 (5), CpHf(mdao)3 (6), CpZr(tdao)3 (7), and CpHf(tdao)3 (8). Thermogravimetric analysis was used for the assessment of the evaporation characteristics of complexes 1, 2, 5, and 6, and it revealed multistep weight losses with high residues. On the other hand, the thermogravimetric analysis curves of complexes 3, 4, 7, and 8 comprising tdao ligands revealed single-step weight losses with moderate residues. Single-crystal X-ray diffraction studies of complexes 1, 3, and 7 showed that all of the complexes have monomeric molecular structures. Complex 7 exhibited a low melting point (75 °C), good volatility, and high thermal stability compared with other complexes. Therefore, an atomic layer deposition process for the growth of ZrO2 was developed by using ZrCp(tdao)3 (7) as a novel precursor.

Synthesis and Volatility Characterization of Mo(II) and W(II) Compounds for Thin Films.

Mo(II) and W(II) compounds, Mo(η3-allyl)(CO)2(Tri-MEDA)Br (1), Mo(η3-allyl)(CO)2(TMEDA)Br (2), W(η3-allyl)(CO)2(Tri-MEDA)Br (3), and W(η3-allyl)(CO)2(TMEDA)Br (4) (Tri-MEDA = N,N,N'-trimethylethylenediamine), were synthesized and characterized. The molecular structures of 1 and 3 were nearly identical with a pseudo-octahedral geometry except for the different Mo and W metal centers. The thermogravimetric analysis of 1 and 3 showed approximately 53 and 64% residues at 550 °C, respectively, which were significantly higher than the values for the expected materials. However, 1 and 3 sublimed at 100 °C under 0.40 Torr and 120 °C under 0.50 Torr, respectively, confirming that they were volatile. For 1 and 3, the temperatures at a vapor pressure of 1 Torr and enthalpies of vaporization (ΔHvap) were 168.78 °C and 143.8 kJ mol-1, and 167.48 °C and 148.5 kJ mol-1, respectively. The tungsten compound (3) exhibited good durability for 5 weeks under a thermal stability test at a sublimation temperature of 120 °C.

Evaluation of tin nitride (Sn3N4) via atomic layer deposition using novel volatile Sn precursors.

Novel Sn precursors, Sn(tbip)2, Sn(tbtp)2, and Sn(tbta)2, were synthesized and characterized using various analytical techniques and density functional theory calculations. These precursors contained cyclic amine ligands derived from iminopyrrolidine. X-ray crystallography revealed the formation of monomeric SnL2 with distorted seesaw geometry. Thermogravimetric analysis demonstrated the exceptional volatility of all complexes. Sn(tbtp)2 showed the lowest residual weight of 2.7% at 265 °C. Sn3N4 thin films were successfully synthesized using Sn(tbtp)2 as the Sn precursor and NH3 plasma. The precursor exhibited ideal characteristics for atomic layer deposition, with a saturated growth per cycle value of 1.9 Å cy-1 and no need for incubation when the film was deposited at 150-225 °C. The indirect optical bandgap of the Sn3N4 film was approximately 1-1.2 eV, as determined through ultraviolet-visible spectroscopy. Therefore, this study suggests that the Sn3N4 thin films prepared using the newly synthesized Sn precursor are suitable for application in thin-film photovoltaic devices.

Novel Volatile Heteroleptic Barium Complexes Using Tetradentate Ligand and ß-Diketonato Ligand.

Novel barium heteroleptic complexes were synthesized through the substitution of the bis(trimethylsilyl)amide of Ba(btsa)2·2DME with aminoalkoxide and ß-diketonate ligands. Compounds [Ba(ddemap)(tmhd)]2 (1) and [Ba(ddemmp)(tmhd)]2 (2) were obtained and analyzed through Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and elemental analysis (ddemapH = 1-(dimethylamino)-5-((2-(dimethylamino)ethyl) (methyl)amino)pentan-3-ol and ddemmpH = 1-(dimethylamino)-5-((2-(dimethylamino)ethyl) (methyl)amino)-3-methylpentan-3-ol). In single-crystal X-ray crystallography, complex 1 exhibited a dimeric structure with µ2-O bonds of the ddemap ligand. All complexes exhibited high volatility and could be sublimed under reduced pressure (0.5 Torr) at 160 °C, indicating that these complexes are promising candidates as atomic layer deposition or chemical vapor deposition precursors for the growth of barium-containing thin films.

Synthesis and Characterization of Tungsten Amide Complexes for the Deposition of Tungsten Disulfide Thin Films.

To substitute corrosive halogen ligands, we designed and synthesized novel tungsten complexes containing amido ligands, W(DMEDA)3 (1) and W(DEEDA)3 (2) (DMEDA = N,N'-dimethylethylenediamido; DEEDA = N,N'-diethylethylenediamido). Complexes 1 and 2 were characterized by 1H NMR, 13C NMR, FT-IR, and elemental analysis. The pseudo-octahedral molecular structure of 1 was confirmed by single-crystal X-ray crystallography. The thermal properties of 1 and 2 were analyzed by thermogravimetric analysis (TGA), which confirmed that the precursors were volatile and exhibited adequate thermal stability. Additionally, the WS2 deposition test was performed using 1 in thermal chemical vapor deposition (thermal CVD). Further analysis of the surface of the thin films was conducted using Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS).

Synthesis of Mononuclear Strontium Complexes with Polyether and ß-Diketonato Ligands.

Strontium ß-diketonate complexes were synthesized by the substitution reaction of the bis(trimethylsilyl) amide of Sr(btsa)2·2DME with an ethereal group and ß-diketonate ligands. The compounds [Sr(tmge)(btsa)]2 (1), [Sr(tod)(btsa)]2 (2), Sr(tmgeH)(tfac)2 (3), Sr(tmgeH)(acac)2 (4), Sr(tmgeH)(tmhd)2 (5), Sr(todH)(tfac)2 (6), Sr(todH)(acac)2 (7), Sr(todH)(tmhd)2 (8), Sr(todH)(hfac)2 (9), Sr(dmts)(hfac)2 (10), [Sr(mee)(tmhd)2]2 (11), and Sr(dts)(hfac)2·DME (12) were obtained and analyzed by various techniques, including FT-IR, NMR, TGA (thermogravimetric analyses), and elemental analysis. Complexes 1, 3, 8, 9, 10, 11, and 12 were further structurally confirmed by single-crystal X-ray crystallography, where complexes 1 and 11 showed dimeric structures with µ2-O bonds of ethereal groups or tmhd ligands, and complexes 3, 8, 9, 10, and 12 displayed monomeric structures. Interestingly, compounds 10 and 12, which preceded trimethylsilylation of the coordinating ethereal alcohols such as tmhgeH and meeH in the presence of HMDS as by-products due to highly increasing acidity of them, originated from electron-withdrawing two hfac ligands.

Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All-In-One Separator.

The uncontrollable dendritic growth of metallic lithium during repeated cycling in carbonate electrolytes is a crucial obstacle hindering the practical use of Li-metal batteries (LMBs). Among numerous approaches proposed to mitigate the intrinsic constraints of Li metal, the design of a functional separator is an attractive approach to effectively suppress the growth of Li dendrites because direct contact with both the Li metal surface and the electrolyte is maintained. Here, a newly designed all-in-one separator containing bifunctional CaCO3 nanoparticles (CPP separator) is proposed to achieve the flattening of Li deposits on the Li electrode. Strong interactions between the highly polar CaCO3 nanoparticles and the polar solvent reduces the ionic radius of the Li+ -solvent complex, thus increasing the Li+ transference number and leading to a reduced concentration overpotential in the electrolyte-filled separator. Furthermore, the integration of CaCO3 nanoparticles into the separator induces the spontaneous formation of mechanically-strong and lithiophilic CaLi2 at the Li/separator interface, which effectively decreases the nucleation overpotential toward Li plating. As a result, the Li deposits exhibit dendrite-free planar morphologies, thus enabling excellent cycling performance in LMBs configured with a high-Ni cathode in a carbonate electrolyte under practical operating conditions.

Amidoxime-Containing Ti Precursors for Atomic Layer Deposition of TiN Thin Films with Suppressed Columnar Microstructure.

This paper reports the synthesis of three novel titanium complexes containing amidoxime ligands as potential precursors for titanium nitride (TiN) thin films fabricated using atomic layer deposition (ALD). A series of ligands, viz., N'-methoxy-N-methylacetimidamide (mnnoH), N'-ethoxy-N-methylacetimidamide (ennoH), and N'-methoxy-N-methylbenzimidamide (pnnoH), were successfully synthesized and used to produce Ti(mnno)(NMe2)3 (4), Ti(enno)(NMe2)3 (5), and Ti(pnno)(NMe2)3 (6). Thermogravimetric analysis curves of complexes 4-6 revealed a single-step weight loss up to 200 °C. Pyrolysis occurred beyond 200 °C. Among the three new complexes, 5 was liquid at room temperature. Therefore, TiN was synthesized by ALD using Ti(enno)(NMe2)3 (5) as a novel precursor. A TiN thin film was deposited from the Ti(enno)(NMe2)3 (5) precursor and NH3 plasma, and self-limiting growth was achieved by varying the injection/purge duration. TiN thin film growths were observed with a growth per cycle (GPC) of 0.05-0.13 nm·cy-1 at deposition temperatures between 150 and 300 °C, while the measured resistivity was as low as 420 µΩ·cm. The high reactivity of the precursor promotes nucleation, resulting in TiN thin films with smooth, good step coverage and preferentially orientated microstructure.

Bi-Morphological Form of SiO2 on a Separator for Modulating Li-Ion Solvation and Self-Scavenging of Li Dendrites in Li Metal Batteries.

The lithium (Li) metal anode is highly desirable for high-energy density batteries. During prolonged Li plating-stripping, however, dendritic Li formation and growth are probabilistically high, allowing physical contact between the two electrodes, which results in a cell short-circuit. Engineering the separator is a promising and facile way to suppress dendritic growth. When a conventional coating approach is applied, it usually sacrifices the bare separator structure and severely increases the thickness, ultimately decreasing the volumetric density. Herein, we introduce dielectric silicon oxide with the feature of bi-morphological form, i.e., backbone-covered and backbone-anchored, onto the conventional polyethylene separator without any volumetric change. These functionally vary the Li+ transference number and the ionic conductivity so as to modulate Li-ion solvation and self-scavenging of Li dendrites. The proposed separator paves the way to maximizing the full cell performance of Li/NCM622 toward practical application.

Hierarchically Porous Ferroelectric Layer with the Aligned Dipole Moment for a High-Performance Aqueous Zn Metal Battery.

Rechargeable aqueous Zn metal batteries (AZMBs) are desirable because of the advantages of metallic Zn and aqueous media. However, AZMBs suffer from limited cyclability and low Coulombic efficiency, originating from uncontrolled dendrite growth and side reactions such as hydrogen gas evolution and corrosion. A hierarchically porous poly(vinylidene difluoride) (PVDF) protection layer with ferroelectric ß-phases is formed on the Zn metal using a simple electrospinning method. This suppresses Zn metal failure modes such as side reactions and dendrite growth and supports rapid electrolyte accessibility. The synergetic effect of hierarchically porous structures and ferroelectricity not only facilitates a supporting matrix to form uniform nucleation sites for Zn deposition but also inhibits corrosion, allowing dendrite-free Zn deposition. This multifunctional PVDF film significantly improves the cyclability of Zn symmetric cells, allowing for up to 850 h of repeated plating/stripping cycles. Moreover, it exhibits an excellent cycle life of 1000 cycles under harsh conditions and high current densities of 4.0-10.0 mA cm-2, which are 62-fold higher than those that the bare Zn electrode tolerates.

Highly Photosensitive Lead Sulfide Thin Films Grown by H2 S Free MOCVD Using a Single Source Metal-Organic Precursor.

High-quality lead sulfide (PbS) films are deposited on selected substrate chemistries by an H2 S-free metal-organic chemical vapor deposition (MOCVD) process using a single-source metal-organic complex (Pb(dmampS)2 ). The complex is synthesized via a salt metathesis reaction between PbCl2  and lithium 1-(dimethylamino)-2-methylpropane-2-thiolate (Li(dmampS)) in diethyl ether. Subsequent film deposition is conducted by a simple thermolysis process in the absence of H2 S, yet chemical and structural analysis confirm chemically stoichiometric and homogenous films. Mechanistic studies with electron impact mass spectroscopy (EIMS) and gas chromatography mass spectroscopy (GCMS) suggest the selective cleavage of C-S bonds in the complex as the reason for the facile PbS formation with negligible impurity incorporation. The high crystallinity, low hole concentrations, and charge transport properties comparable and in many cases superior to films produced by atomic layer deposition (ALD) testify to the quality of the films. Lastly, rigid and flexible photodetectors fabricated with the PbS films exhibit considerably high photocurrents, reliable switching characteristics, and high sensitivity over a broad spectral bandwidth, highlighting the potential for realizing practical broadband photodetectors.

Novel Heteroleptic Tin(II) Complexes Capable of Forming SnO and SnO2 Thin Films Depending on Conditions Using Chemical Solution Deposition.

A new heteroleptic complex series of tin was synthesized by the salt metathesis reaction of SnX2 (X = Cl, Br, and I) with aminoalkoxide and various N-alkoxy-functionalized carboxamide ligands. The complexes, [ClSn(dmamp)]2 (1), [BrSn(dmamp)]2 (2), and [ISn(dmamp)]2 (3), were prepared from the salt metathesis reaction of SnX2 with one equivalent of dmamp; [Sn(dmamp)(empa)]2 (4), [Sn(dmamp)(mdpa)]2 (5), and [Sn(dmamp)(edpa)]2 (6) were prepared via the salt metathesis reaction using complex 2 with one equivalent of N-alkoxy-functionalized carboxamide ligand. Complexes 1-5 displayed dimeric molecular structures with tin metal centers interconnected by µ2-O bonding via the alkoxy oxygen atom. The molecular structures of complexes 1-5 showed distorted trigonal bipyramidal geometries with lone pair electrons in the equatorial position. Using complex 6 as a tin precursor, SnO x films were deposited by chemical solution deposition (CSD) and subsequent post-deposition annealing (PDA) at high temperatures. SnO and SnO2 films were selectively obtained under controlled PDA atmospheres of argon and oxygen, respectively. The SnO films featured a tetragonal romarchite structure with high crystallinity and a preferred growth orientation along the (101) plane. They also exhibited a lower transmittance of >52% at 400 nm due to an optical band gap of 2.9 eV. In contrast, the SnO2 films exhibited a tetragonal cassiterite crystal structure and an extremely high transmittance of >97% at 400 nm was observed with an optical band gap of 3.6 eV.

Group IV Transition Metal (M = Zr, Hf) Precursors for High-κ Metal Oxide Thin Films.

This paper describes the synthesis of eight novel zirconium and hafnium complexes containing N-alkoxy carboxamidate-type ligands, as potential precursors for metal oxides and atomic layer deposition (ALD) for HfO2. A series of ligands, viz., N-ethoxy-2,2-dimethylpropanamide (edpaH), N-ethoxy-2-methylpropanamide (empaH), and N-methoxy-2,2-dimethylpropanamide (mdpaH), were used to afford complexes Zr(edpa)4 (1), Hf(edpa)4 (2), Zr(empa)4 (3), Hf(empa)4 (4), Zr(mdpa)4 (5), Hf(mdpa)4 (6), ZrCp(edpa)3 (7), and HfCp(edpa)3 (8). Thermogravimetric analysis curves assessed for the evaporation characteristics of complexes 1-8 revealed single-step weight losses with low residues, except for the mdpa-containing complexes. Single-crystal X-ray diffraction studies of 1, 2, 5, and 6 revealed that all the complexes have monomeric molecular structures, with the central metal ion surrounded by eight oxygen atoms from the four bidentate alkoxyalkoxide ligands. Among the complexes prepared, 8 exhibited a low melting point (64 °C), good volatility (1 Torr at 112 °C), high thermal stability, and excellent endurance over 6 weeks at 120 °C. Therefore, an ALD process for the growth of HfO2 was developed using HfCp(edpa)3 (8) as a novel precursor. Furthermore, the HfO2 film exhibited a low capacitance equivalent oxide thickness of ∼1.5 nm, with Jg as low as ∼3 × 10-4 A/cm2 at Vg -1 V in a metal-insulator-semiconductor capacitor (Au/HfO2/p-Si).

New Volatile Tantalum Imido Precursors with Carboxamide Ligands.

A series of Ta(V) t Bu-imido/N-alkoxy carboxamide complexes, TaCl2(N t Bu)(pyridine)(edpa) (1), TaCl(N t Bu)(edpa)2 (2), Ta(N t Bu)(edpa)3 (3), TaCl2(N t Bu)(pyridine)(mdpa) (4), and Ta(N t Bu)(mdpa)3 (5), were successfully synthesized by metathesis reactions between Ta(N t Bu)Cl3(py)2 and several equivalents of Na(edpa) (edpaH = N-ethoxy-2,2-dimethylpropanamide) and Na(mdpa) (mdpaH = N-methoxy-2,2-dimethylpropanamide). Furthermore, complexes 3 and 5 were simply transformed to new dimeric structures [Ta(µ2-O)(edpa)3]2 (6) and [Ta(µ2-O)(mdpa)3]2 (7) with the elimination of the N t Bu imido group by air exposure. Compounds 1-7 were characterized by 1H and 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis (TGA), and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that complexes 3 and 5 have a distorted pentagonal bipyramidal geometry around the central Ta atom, with three monoanionic bidentate N-alkoxy carboxamide ligands and one t Bu imido ligand saturating the coordination of tantalum ions. TGA revealed that complexes 3 and 5 had superior thermal characteristics and stability. These complexes could potentially be applied as precursors for tantalum oxide thin films.

Synthesis and Crystal Structures of New Strontium Complexes with Aminoalkoxy and ß-Diketonato Ligands.

New heteroleptic strontium complexes were synthesized using substitution reaction of bis(trimethylsilyl)amide of Sr(btsa)2·2DME with aminoalkoxide and ß-diketonate ligands. The complexes [Sr(bdmp)(btsa)]2·2THF (1), [Sr(bdeamp)(btsa)]2 (2), [Sr(dadamb)(btsa)]2 (3), [Sr(bdmp)(hfac)]3 (4), [Sr(bdeamp)(hfac)]3 (5), [Sr(dadamb)(hfac)]3 (6), and [Sr3(dadamb)4(tmhd)2] (7) were prepared and characterized by means of various analysis techniques such as Fourier transform infrared, NMR, thermogravimetric analysis, and elemental analysis. Complexes 1-3 were further structurally confirmed by single-crystal X-ray crystallography, and they displayed dimeric structures in which strontium atoms were connected by alkoxide oxygen atoms of the µ2 type. Compound 1 has a trigonal prismatic structure, whereas 2 and 3 have a distorted square pyramidal structure. In complexes 5-7, trimeric structures were obtained with strontium atoms connected by µ3-O bonds of alkoxide oxygen atoms and µ2-O bonds of alkoxide and ß-diketonate oxygen atoms. The crystal structures of 5, 6, and 7 showed distorted capped octahedral geometry, while 7 (middle Sr atom) displayed a distorted trigonal prism geometry. Complexes 5-7 displayed ∼70% mass loss in the temperature range from 25 to 315 °C.

Synthesis and characterization of novel zinc precursors for ZnO thin film deposition by atomic layer deposition.

A novel series of zinc complexes, [EtZn(dab)]2 (1), [EtZn(damb)]2 (2), [EtZn(damp)]2 (3), and [EtZn(dadb)]2 (4), were prepared via single-step substitution. Further, these were analyzed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, single crystal X-ray diffraction analysis, and thermogravimetric analysis (TGA). The X-ray crystallography analysis revealed that all complexes exist as dimeric structures with distorted tetrahedral geometry having zinc centers that are interconnected via µ2-O bonding of the aminoalkoxy oxygen atom. TGA and thermal analysis of the complexes showed high volatilities and stabilities at sublimation temperatures of 70, 95, 90, and 105 °C at 0.5 Torr for the respective compounds. Precursor 3 was successfully used for ZnO thin film deposition by ALD. A growth rate per cycle (GPC) of 0.125 nm per cycle was obtained at 200 °C and XPS analysis confirmed the growth of highly pure ZnO films without carbon and nitrogen impurities, while XRD analysis revealed the deposition of reasonably crystalline films. Additionally, the high transmittance and wide bandgap of the films are suitable for optoelectronic applications.

Tin(II) Aminothiolate and Tin(IV) Aminothiolate Selenide Compounds as Single-Source Precursors for Tin Chalcogenide Materials.

Tin aminothiolate compounds SnII(dmampS)2 (1) and SnIV(dmampS)2Se (2), where dmampS = 1-(dimethylamino)-2-methylpropane-2-thiolate, were synthesized. The molecular structures of 1 and 2 reveal a seesaw and distorted trigonal-bipyramidal geometry, respectively. The 1H NMR spectrum of 1 shows two types of resonances for the methyl groups of the α-carbon, methyl groups of the amino groups, and methylene groups at room temperature. On the other hand, the 1H NMR spectrum of 2 exhibits a single resonance for each of these groups. According to variable-temperature 1H NMR analysis, each of these two types of resonances occurring at relatively low temperatures (under 223 K for 1 and under 333 K for 2) are merged as a single resonance with increasing temperature. By using thermogravimetric and thermal decomposition analyses, the residual materials of compounds 1 and 2 are confirmed to be SnS and SnSSe, respectively. Compound 1 was subjected to a metal-organic chemical vapor deposition process, which allowed for the deposition of a dense and well-faceted orthorhombic phase SnS thin film on a SiO2/Si substrate with ∼200 nm thickness.

Heteroleptic manganese compounds as potential precursors for manganese based thin films and nanomaterials.

Heteroleptic manganese compounds, [Mn(tmhd)(TMEDA)Cl]2 (1), [Mn(tmhd)(dmamp)]2 (2), Mn2(tmhd)2(edpa)2(µ-THF) (3), [Mn(dmampea)(NEt2)]2 (4), and Mn(dmampea)(iPr-MeAMD) (5), were synthesized and characterized. Compound 5 was a volatile liquid. Structural analysis revealed that 1-4 were dimers. Compounds 1 and 3, 2, and 4 had distorted octahedral, distorted trigonal-bipyramidal, and distorted tetrahedral geometries around the Mn centers, respectively. Based on thermogravimetric analysis, the residues of 2 and 3 were expected to be MnO and Mn3O4, respectively. According to thermogravimetric analysis, 4 showed a higher residual value, whereas 5 exhibited a lower value than those expected for manganese nitrides.