| 1. |
- Buttera, Sydney C., et al.
(författare)
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Resolving Impurities in Atomic Layer Deposited Aluminum Nitride through Low Cost, High Efficiency Precursor Design
- 2021
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 60:15, s. 11025-11031
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Tidskriftsartikel (refereegranskat)abstract
- A heteroleptic amidoalane precursor is presented as a more suitably designed candidate to replace trimethylaluminum (TMA) for atomic layer deposition of aluminum nitride (AlN). The lack of C-Al bonds and the strongly reducing hydride ligands in [AlH2(NMe2)](3) (1) were specifically chosen to limit impurities in target aluminum nitride (AlN) films. Compound 1 is made in a high yield, scalable synthesis involving lithium aluminum hydride and dimethylammonium chloride. It has a vapor pressure of 1 Torr at 40 degrees C and evaporates with negligible residual mass in thermogravimetric experiments. Ammonia (NH3) plasma and 1 in an atomic layer deposition (ALD) process produced crystalline AlN films above 200 degrees C with an Al:N ratio of 1.04. Carbon and oxygen impurities in resultant AlN films were reduced to <1% and <2%, respectively. By using a precursor with a rational and advantageous design, we can improve the material quality of AlN films compared to those deposited using the industrial standard trimethylaluminum and could reduce material cost by up to 2 orders of magnitude.
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| 2. |
- Buttera, Sydney C., et al.
(författare)
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Thermal study of an indium trisguanidinate as a possible indium nitride precursor
- 2018
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 36:1
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Tidskriftsartikel (refereegranskat)abstract
- Tris-N,N,-dimethyl-N,N -diisopropylguanidinatoindium(III) has been investigated both as a chemical vapor deposition precursor and an atomic layer deposition precursor. Although deposition was satisfactory in both cases, each report showed some anomalies in the thermal stability of this compound, warrenting further investigation, which is reported herein. The compound was found to decompose to produce diisopropylcarbodiimide both by computational modeling and solution phase nuclear magnetic resonance characterization. The decomposition was shown to have an onset at approximately 120 degrees C and had a constant rate of decomposition from 150 to 180 degrees C. The ultimate decomposition product was suspected to be bisdimethylamidoN, N,-dimethyl-N,N -diisopropylguanidinato-indium(III), which appeared to be an intractable, nonvolatile polymer. Published by the AVS.
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| 3. |
- 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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| 4. |
- Rouf, Polla, 1993-, et al.
(författare)
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Epitaxial GaN using Ga(NMe2)3 and NH3 plasma by Atomic Layer Deposition
- 2020
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 8:25, s. 8457-8465
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Tidskriftsartikel (refereegranskat)abstract
- Low temperature deposition of high-quality epitaxial GaN is crucial for its integration in electronic applications. Chemical vapor deposition at approximately 800 °C using SiC with an AlN buffer layer or nitridized sapphire as substrate is used to facilitate the GaN growth. Here, we present a low temperature atomic layer deposition (ALD) process using tris(dimethylamido)gallium(III) with NH3 plasma. The ALD process shows self-limiting behaviour between 130–250 °C with a growth rate of 1.4 Å per cycle. The GaN films produced were crystalline on Si (100) at all deposition temperatures with a near stochiometric Ga/N ratio with low carbon and oxygen impurities. When GaN was deposited on 4H-SiC, the films grew epitaxially without the need for an AlN buffer layer, which has never been reported before. The bandgap of the GaN films was measured to be ∼3.42 eV and the Fermi level showed that the GaN was unintentionally n-type doped. This study shows the potential of ALD for GaN-based electronic devices.
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| 5. |
- 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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| 6. |
- Rönnby, Karl, et al.
(författare)
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Methylamines as Nitrogen Precursors in Chemical Vapor Deposition of Gallium Nitride
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:11, s. 6701-6710
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Tidskriftsartikel (refereegranskat)abstract
- Chemical vapor deposition (CVD) is one of the most important techniques for depositing thin films of the group 13 nitrides (13-Ns), AIN, GaN, InN, and their alloys, for electronic device applications. The standard CVD chemistry for 13-Ns uses ammonia as the nitrogen precursor; however, this gives an inefficient CVD chemistry, forcing N/13 ratios of 100/1 or more. Here, we investigate the hypothesis that replacing the N-H bonds in ammonia with weaker N-C bonds in methylamines will permit better CVD chemistry, allowing lower CVD temperatures and an improved N/13 ratio. Quantum chemical computations show that while the methylamines have a more reactive gas-phase chemistry, ammonia has a more reactive surface chemistry. CVD experiments using methylamines failed to deposit a continuous film, while instead micrometer-sized gallium droplets were deposited. This study shows that the nitrogen surface chemistry is most likely more important to be considered than the gas-phase chemistry when searching for better nitrogen precursors for 13-N CVD.
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| 7. |
- 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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| 8. |
- 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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