| 1. |
- O´brien, Nathan, et al.
(författare)
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In Situ Activation of an Indium(III) Triazenide Precursor for Epitaxial Growth of Indium Nitride by Atomic Layer Deposition
- 2020
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 32:11, s. 4481-4489
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Tidskriftsartikel (refereegranskat)abstract
- Indium nitride (InN) is characterized by its high electron mobility, making it a ground-breaking material for high frequency electronics. The difficulty of depositing high-quality crystalline InN currently impedes its broad implementation in electronic devices. Herein, we report a new highly volatile In(III) triazenide precursor and demonstrate its ability to deposit high-quality epitaxial hexagonal InN by atomic layer deposition (ALD). The new In(III) precursor, the first example of a homoleptic triazenide used in a vapor deposition process, was easily synthesized and purified by sublimation. Thermogravimetric analysis showed single step volatilization with an onset temperature of 145 degrees C and negligible residual mass. Strikingly, two temperature intervals with self-limiting growth were observed when depositing InN films. In the high-temperature interval, the precursor underwent a gas-phase thermal decomposition inside the ALD reaction chamber to produce a more reactive In(III) compound while retaining self-limiting growth behavior. Density functional theory calculations revealed a unique two-step decomposition process, which liberates three molecules of each propene and N-2 to give a smaller tricoordinated In(III) species. Stoichiometric InN films with very low levels of impurities were grown epitaxially on 4H-SiC. The InN films deposited at 325 degrees C had a sheet resistivity of 920 Omega/sq. This new triazenide precursor enables ALD of InN for semiconductor applications and provides a new family of M-N bonded precursors for future deposition processes.
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| 2. |
- Rouf, Polla, et al.
(författare)
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Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition
- 2021
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 33:9, s. 3266-3275
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Tidskriftsartikel (refereegranskat)abstract
- Gallium nitride (GaN) is the main component of modern-day high electron mobility transistors due to its favorable electronic properties. As electronic devices become smaller with more complex surface architecture, the ability to deposit high-quality GaN films at low temperatures is required. Herein, we report a new highly volatile Ga(III) triazenide precursor and demonstrate its ability to deposit high-quality epitaxial GaN by atomic layer deposition (ALD). This new Ga(III) triazenide, the first hexacoordinated Ga-N bonded precursor used in a vapor deposition process, was easily synthesized and purified by either sublimation or recrystallisation. Thermogravimetric analysis showed single-step volatilization with an onset temperature of 155 degrees C and negligible residual mass. Three temperature intervals with self-limiting growth were observed when depositing GaN films. The GaN films grown in the second growth interval at 350 degrees C were epitaxial on 4H-SiC without an AlN seed layer and found to have a near stoichiometric Ga/N ratio with very low levels of impurities. In addition, electron microstructure analysis showed a smooth film surface and a sharp interface between the substrate and film. The band gap of these films was 3.41 eV with the Fermi level at 1.90 eV, showing that the GaN films were unintentionally n-type-doped. This new triazenide precursor enables ALD of GaN for semiconductor applications and provides a new Ga(III) precursor for future deposition processes.
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| 3. |
- Rouf, Polla, et al.
(författare)
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The Endocyclic Carbon Substituent of Guanidinate and Amidinate Precursors Controlling Atomic Layer Deposition of InN Films
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:42, s. 25691-25700
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Tidskriftsartikel (refereegranskat)abstract
- Indium nitride (InN) is an interesting material for future high-frequency electronics due to its high electron mobility. The problematic deposition of InN films currently prevents full exploration of InN-based electronics. We present studies of atomic layer deposition (ALD) of InN using In precursors with bidentate ligands forming In-N bonds: tris(N,N-dimethyl-N,N -diisopropylguanidinato)indium(III), tris(N,N-diisopropylamidinato)indium(III), and tris(N,N-diisopropylformamidinato)indium(III). These compounds form a series were the size of the substituent on the endocyclic position decreases from -NMe2 to -Me and to -H, respectively. We show that when the size of the substituent decreases, the InN films deposited have a better crystalline quality, of better optical quality, lower roughness, and an In/N ratio closer to unity. From quantum chemical calculations, we show that the smaller substituents lead to less steric repulsion and weaker bonds between the ligand and In center. We propose that these effects render a more favored surface chemistry for the nitridation step in the ALD cycle, which explains the improved film properties.
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| 4. |
- Samii, Rouzbeh, 1986-
(författare)
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Group 11–14 Triazenides : Synthesis, characterization, and thermal evaluation for use in chemical vapor deposition
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are corner-stone techniques for depositing thin films in semi-conductor manufacturing. To deposit semiconductor grade materials, these techniques rely on high-performance precursors. This thesis covers synthesis, characterization, and evaluation of 1,3-dialkyltriazenides of group 11–14 metals as precursors for CVD and ALD. Triazenides had previously not been used as precursors for ALD, nor any other CVD process. The gallium and indium triazenides were used for ALD of indium- and gallium nitride and yielded materials of superior quality over other precursors. The success of these precursors sparked subsequent investigation into triazenides of zinc, and the group 11- and 14 metals. These triazenides showed high volatility and thermal stability making them highly interesting as CVD and ALD precursors.
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| 5. |
- Samii, Rouzbeh, et al.
(författare)
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Synthesis and Thermal Study of Hexacoordinated Aluminum(III) Triazenides for Use in Atomic Layer Deposition
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society. - 0020-1669 .- 1520-510X. ; 60:7, s. 4578-4587
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Tidskriftsartikel (refereegranskat)abstract
- Amidinate and guanidinate ligands have been used extensively to produce volatile and thermally stable precursors for atomic layer deposition. The triazenide ligand is relatively unexplored as an alternative ligand system. Herein, we present six new Al(III) complexes bearing three sets of a 1,3-dialkyltriazenide ligand. These complexes volatilize quantitatively in a single step with onset volatilization temperatures of similar to 150 degrees C and 1 Torr vapor pressures of similar to 134 degrees C. Differential scanning calorimetry revealed that these Al(III) complexes exhibited exothermic events that overlapped with the temperatures of their mass loss events in thermogravimetric analysis. Using quantum chemical density functional theory computations, we found a decomposition pathway that transforms the relatively large hexacoordinated Al(III) precursor into a smaller dicoordinated complex. The pathway relies on previously unexplored interligand proton migrations. These new Al(III) triazenides provide a series of alternative precursors with unique thermal properties that could be highly advantageous for vapor deposition processes of Al containing materials.
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| 6. |
- Samii, Rouzbeh, et al.
(författare)
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Synthesis, characterisation and reactivity of a zinc triazenide for potential use in vapour deposition
- 2024
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Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 53:13, s. 5911-5916
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we synthesised and characterised a new zinc(ii) triazenide for potential use in vapour deposition of zinc sulphide thin films. The compound is volatile and quantitatively sublimes at 80 degrees C under vacuum (0.5 mbar). Thermogravimetric analysis showed a one-step volatilisation with an onset temperature at similar to 125 degrees C and 5% residual mass. The compound also reacted with 2 or 4 molar equivalents of triphenylsilanethiol to give dimeric and monomeric zinc thiolates, respectively. The high volatility, thermal stability, and reactivity with sterically hindered thiols makes this compound a potential candidate for use in vapour deposition of zinc containing thin films. Herein, we synthesise and characterise a new volatile and thermally stable Zn(ii) triazenide. We also react it with a bulky thiol to give two different Zn(ii) thiolates. This new triazenide shows high promise as a precursor for vapour deposition of ZnS thin films.
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| 7. |
- Samii, Rouzbeh, et al.
(författare)
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Synthesis, Characterization, and Thermal Study of Divalent Germanium, Tin, and Lead Triazenides as Potential Vapor Deposition Precursors
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:17, s. 12759-12765
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Tidskriftsartikel (refereegranskat)abstract
- Only a few M-N bonded divalent group 14 precursors are available for vapor deposition, in particular for Ge and Pb. A majority of the reported precursors are dicoordinated with the Sn(II) amidinates, the only tetracoordinated examples. No Ge(II) and Pb(II) amidinates suitable for vapor deposition have been demonstrated. Herein, we present tetracoordinated Ge(II), Sn(II), and Pb(II) complexes bearing two sets of chelating 1,3-di-tert-butyltriazenide ligands. These compounds are thermally stable, sublime quantitatively between 60 and 75 degrees C (at 0.5 mbar), and show ideal single-step volatilization by thermogravimetric analysis.
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| 8. |
- Samii, Rouzbeh, 1986-, et al.
(författare)
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Synthesis, Structure, and Thermal Properties of Volatile Group 11 Triazenides as Potential Precursors for Vapor Deposition
- 2022
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 61:51, s. 20804-20813
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Tidskriftsartikel (refereegranskat)abstract
- Group 11 thin films are desirable as interconnects in microelectronics. Although many M-N-bonded Cu precursors have been explored for vapor deposition, there is currently a lack of suitable Ag and Au derivatives. Herein, we present monovalent Cu, Ag, and Au 1,3-di-tert-butyltriazenides that have potential for use in vapor deposition. Their thermal stability and volatility rival that of current state-of-the-art group 11 precursors with bidentate M-N-bonded ligands. Solution-state thermolysis of these triazenides yielded polycrystalline films of elemental Cu, Ag, and Au. The compounds are therefore highly promising as single-source precursors for vapor deposition of coinage metal films.
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| 9. |
- Samii, Rouzbeh, 1986-, et al.
(författare)
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Synthesis, Structure and Thermal Properties of Volatile Indium and Gallium Triazenides
- 2022
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley-V C H Verlag GMBH. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :24
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Tidskriftsartikel (refereegranskat)abstract
- Indium and gallium nitride are important semi-conductor materials with desirable properties for high-frequency and power electronics. We have previously demonstrated high-quality ALD grown InN and GaN using the hexacoordinated 1,3-diisopropyltriazenide In(III) and Ga(III) precursors. Herein we report the structural and thermal properties their analogues employing combinations of isopropyl, sec-butyl and tert-butyltriazenide alkyl groups on the exocyclic nitrogen of the triazenide ligand. The new triazenide compounds were all found to be volatile (80-120 degrees C, 0.5 mbar) and showed very good thermal stability (200 and 300 degrees C). These new triazenide analogues provide a set of precursors whose thermal properties are determined and can be accordingly tailored by strategic choice of exocyclic nitrogen alkyl substituents.
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