Synthesis, Structure and Thermal Properties of Volatile Indium and Gallium Triazenides

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

Synthesis and Thermal Study of Hexacoordinated Aluminum(III) Triazenides for Use in Atomic Layer Deposition

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

Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

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

Group 11–14 Triazenides : Synthesis, characterization, and thermal evaluation for use in chemical vapor deposition

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.

Synthesis, Structure and Thermal Properties of Volatile Indium and Gallium Triazenides

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.Funding Agencies|Swedish foundation for Strategic Research [SSF-RMA 15-0018]; Knut and Alice Wallenberg foundation [KAW 2013.0049]</p

Synthesis, Structure and Thermal Properties of Volatile Indium and Gallium Triazenides

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 di-isopropyltriazenide 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 ºC, 0.5 mbar) and showed very good thermal stability (200 and 300 °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

Synthesis, Structure, and Thermal Properties of Volatile Group 11 Triazenides as Potential Precursors for Vapor Deposition

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.Funding Agencies|Swedish foundation for Strategic Research [SSF-RMA 15-0018]; Knut and Alice Wallenberg foundation [KAW 2013.0049]; Swedish Research Council (VR); Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University [2009 00971]</p

Synthesis and Thermal Study of Hexacoordinated Aluminum(III) Triazenides for Use in Atomic Layer Deposition

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 ~150 °C and 1 Torr vapor pressures of ~134 °C. Differential scanning calorimetry revealed 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 transforming the relatively large hexacoordinated Al(III) precursor into a smaller dicoordinated complex. The pathway relies on previously unexplored inter-ligand interactions, in which protons migrate between the triazenide ligands. These new Al(III) triazenides provides a series of alternative precursors with unique thermal properties that could be highly advantageous for vapor deposition processes of Al containing materials.</p

The Endocyclic Carbon Substituent of Guanidinate and Amidinate Precursors Controlling Atomic Layer Deposition of InN Films

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.Funding Agencies|Swedish foundation for Strategic Research through the project "Time-resolved low temperature CVD for III-nitrides" [SSF-RMA 15-0018]; Knut and Alice Wallenberg foundation through the project "Bridging the THz gap" [KAW 2013.0049]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]</p

Differences in the MRI Signature and ADC Values of Diffuse Midline Gliomas with H3 K27M Mutation Compared to Midline Glioblastomas

We conducted a two-center retrospective survey on standard MRI features including apparent diffusion coefficient mapping (ADC) of diffuse midline gliomas H3 K27M-mutant (DMG) compared to midline glioblastomas H3 K27M-wildtype (midGBM-H3wt). We identified 39 intracranial DMG and 18 midGBM-H3wt tumors. Samples were microscopically re-evaluated for microvascular proliferations and necrosis. Image analysis focused on location, peritumoral edema, degree of contrast enhancement and DWI features. Within DMG, MRI features between tumors with or without histomorphological GBM features were compared. DMG occurred in 15/39 samples from the thalamus (38%), in 23/39 samples from the brainstem (59%) and in 1/39 tumors involving primarily the cerebellum (2%). Edema was present in 3/39 DMG cases (8%) versus 78% in the control (midGBM-H3wt) group (p &lt; 0.001). Contrast enhancement at the tumor rim was detected in 17/39 DMG (44%) versus 67% in control (p = 0.155), and necrosis in 24/39 (62%) versus 89% in control (p = 0.060). Strong contrast enhancement was observed in 15/39 DMG (38%) versus 56% in control (p = 0.262). Apparent diffusion coefficient (ADC) histogram analysis showed significantly higher skewness and kurtosis values in the DMG group compared to the controls (p = 0.0016/p = 0.002). Minimum relative ADC (rADC) values, as well as the 10th and 25th rADC-percentiles, were lower in DMGs with GBM features within the DMG group (p &lt; 0.001/p = 0.012/p = 0.027). In conclusion, DMG cases exhibited markedly less edema than midGBM-H3wt, even if histomorphological malignancy was present. Histologically malignant DMGs and midGBM-H3wt more often displayed strong enhancement, as well as rim enhancement, than DMGs without histomorphological malignancy. DMGs showed higher skewness and kurtosis values on ADC-histogram analysis compared to midGBM-H3wt. Lower minimum rADC values in DMGs indicated malignant histomorphological features, likely representing a more complex tissue microstructure