Atomic Layer Deposition of Tin Monosulfide Thin Films

Thin film solar cells made from earth-abundant, non-toxic materials are needed to replace the current technology that uses $Cu(In,Ga)(S,Se)_2$ and $CdTe$, which contain scarce and toxic elements. One promising candidate absorber material is tin monosulfide ($SnS$). In this report, pure, stoichiometric, single-phase SnS films were obtained by atomic layer deposition (ALD) using the reaction of $bis(N,N′-diisopropylacetamidinato)tin(II)$ $[Sn(MeC(N-^{i}Pr)_{2})_{2}]$ and hydrogen sulfide $(H_2 S)$ at low temperatures (100 to 200 $°C$). The direct optical band gap of SnS is around 1.3 eV and strong optical absorption $(\alpha > 10^4 cm^{−1})$ is observed throughout the visible and near-infrared spectral regions. The films are p-type semiconductors with carrier concentration on the order of $10^{16} cm^{−3}$ and hole mobility $0.82–15.3cm^{2}V^{−1}s^{−1}$ in the plane of the films. The electrical properties are anisotropic, with three times higher mobility in the direction through the film, compared to the in-plane direction.Chemistry and Chemical Biolog

(Sn,Al)Ox(Sn,Al)O_x Films Grown by Atomic Layer Deposition

$(Sn,Al)O_x$ composite films with various aluminum (Al) to tin (Sn) ratios were deposited using an atomic layer deposition technique. The chemisorption behavior of cyclic amide of tin(II) and trimethylaluminum were analyzed by Rutherford backscattering spectroscopy. Both precursors showed retarded and enhanced chemisorption on $Al_2O_3$ and $SnO_2$ surfaces, respectively. The films show highly anisotropic electrical conductivity, i.e., much higher resistivity in the direction through the film than parallel to the surface of the film. The cause of the anisotropy was investigated by cross-sectional transmission electron microscopy, which showed a nanolaminate structure of crystalline $SnO_2$ grains separated by thin, amorphous $Al_2O_3$ monolayers. When the Al concentration was higher than $\sim 35$ atom percent, the composite films became amorphous, and the vertical and lateral direction resistivity values converged toward one value. By properly choosing the ratio of $SnO_2$ and $Al_2O_3$ subcycles, controlled adjustment of film electrical resistivity over more than 15 orders of magnitude was successfully demonstrated.Chemistry and Chemical Biolog

Atomic layer deposition of lanthanum oxide with heteroleptic cyclopentadienyl-amidinate lanthanum precursor - Effect of the oxygen source on the film growth and properties

La2O3 thin films were deposited by atomic layer deposition from a liquid heteroleptic La precursor, La(iPrCp)2(iPr-amd), with either water, ozone, ethanol, or both water and ozone (separated by a purge) as the oxygen source. The effect of the oxygen source on the film growth rate and properties such as crystallinity and impurities was studied. Saturation of the growth rate was achieved at 225 °C with O3 as the oxygen source. With water, very long purge times were used due to the hygroscopicity of La2O3 but saturation of the growth rate was not achieved. Interestingly, when an O3 pulse was added after the water pulse with a purge in between, the growth rate decreased and the growth saturated at 200 °C. With ethanol lanthanum hydroxide was formed instead of La2O3 at 200–275 °C whereas hexagonal La2O3 films were obtained at 300 °C but the growth was not saturative. Using the separate pulses of water and ozone in the same deposition provided the best results from the four studied deposition processes. After annealing the films deposited with the La(iPrCp)2(iPrAMD)/H2O/O3 process showed pure hexagonal phase in all the films regardless of the deposition temperature, whereas mixtures of cubic and hexagonal La2O3 were seen with the other processes.Peer reviewe

Toward epitaxial ternary oxide multilayer device stacks by atomic layer deposition

The authors demonstrate multilayer epitaxial films by atomic layer deposition and postdeposition annealing. Their example features two ABO(3) type perovskite oxide films with different materials properties-a conductor (LaNiO3) and an insulator (SrTiO3)-that can be integrated epitaxially once the geometric interaction between the two oxides' lattices is understood. Once preliminary epitaxial materials had been developed, the pilot multilayer device fabricated was an epitaxial metal-insulator-metal structure with layers of similar to 5 nm thickness. This work shows the potential for advanced device types based on epitaxial atomic layer deposited films, assuming that care is taken in the selection of processes and starting substrate. Published by the AVS.Peer reviewe

Comparative study on the use of novel heteroleptic cyclopentadienyl-based zirconium precursors with H2O and O-3 for atomic layer deposition of ZrO2

Three heteroleptic Zr precursors were studied for atomic layer deposition (ALD) of ZrO2. Films were deposited from Zr(Cp)((t)BuDAD)((OPr)-Pr-i), Zr(MeCp)(TMEA), and Zr(Me5Cp)(TEA) with either water or ozone as the oxygen source {tBuDAD = N, N-bis(tertbutyl) ethene-1,2-diaminato, TMEA = tris[2-(methylamino) ethyl]aminate, TEA = triethoanolaminate}. Self-limiting film growth was confirmed for the Zr(Cp)((t)BuDAD)((OPr)-Pr-i)/O-3 process at 250 degrees C and for the Zr(M(e)5Cp)(TEA)/O-3 process at 375 degrees C, which is among the highest temperatures for advanced heteroleptic precursors. Excellent film purity with C, H, and N levels below the detection limit of the elastic recoil detection analysis was obtained with ozone as the oxygen source. All the studied processes showed the same trend that at low deposition temperatures films were tetragonal ZrO2 and at higher temperatures mixtures of tetragonal and monoclinic ZrO2. With water, the monoclinic phase appeared at higher temperatures than with ozone. In addition to the deposition temperature, the film thickness affected the phase; thinner films favored the tetragonal phase and monoclinic peaks were more clearly seen in thicker films. The high thermal stability and excellent film purity show that from the three studied Zr precursors, Zr(Me5Cp)(TEA) is a noteworthy precursor candidate for ALD of ZrO2. Published by the AVS.Peer reviewe

Synthesis and Characterization of Organometallic Compounds for Materials

181 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.A series of BH3PR2BH3- (R =H, Ph, t-Bu) were synthesized and characterized. Treatment of the adduct PH3·BH3 with excess NaBH4 in THF afforded a white powder, Na(BH3PH2BH 3). Reactions of Na(BH3PH2BH3) and Li(BH3PPh2BH3)·diox with several metal halides were described.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Synthesis and Characterization of Organometallic Compounds for Materials

181 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.A series of BH3PR2BH3- (R =H, Ph, t-Bu) were synthesized and characterized. Treatment of the adduct PH3·BH3 with excess NaBH4 in THF afforded a white powder, Na(BH3PH2BH 3). Reactions of Na(BH3PH2BH3) and Li(BH3PPh2BH3)·diox with several metal halides were described.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Thermal Atomic Layer Deposition of Yttrium Oxide Films and Their Properties in Anticorrosion and Water Repellent Coating Applications

The thermal atomic layer deposition (ThALD) of yttrium oxide (Y2O3) was developed using the newly designed, liquid precursor, Y(EtCp)2(iPr2-amd), as the yttrium source in combination with different oxygen sources, such as ozone, water and even molecular oxygen. Saturation was observed for the growth of the Y2O3 films within an ALD window of 300 to 450 °C and a growth per cycle (GPC) up to 1.1 Å. The resulting Y2O3 films possess a smooth and crystalline structure, while avoiding any carbon and nitrogen contamination, as observed by X-ray photoelectron spectroscopy (XPS). The films showed strong resistance to fluorine-containing plasma, outperforming other resistant materials, such as silicon oxide, silicon nitride and alumina. Interestingly, the hydrophilic character exhibited by the film could be switched to hydrophobic after exposure to air, with water contact angles exceeding 90°. After annealing under N2 flow at 600 °C for 4 min, the hydrophobicity was lost, but proved recoverable after prolonged air exposure or intentional hydrocarbon exposure. The origin of these changes in hydrophobicity was examined