University of Michigan
Project Leader – QuMat.1-TUE-3.3A
Synthesis of artificially engineered unit cells for quantum anomalous Hall effect
Brief research summary over last 5 years / academic profile
In the last five years the Bol group has pioneered atomic layer deposition (ALD) for the synthesis of 2D materials. ALD is a scalable, low temperature preparation method for thin films that offers precise thickness control down to the sub-monolayer and can therefore be instrumental for the large area synthesis of 2D materials. The current focus is on ALD of 2D transition metal dichalcogenides (2D-TMDs).
The group’s first results in this area demonstrate (Nanoscale 2018) that it is possible to obtain excellent control over the layer thickness down to a monolayer over a large area (4-inch wafer), showcasing ALD’s potential for the fabrication of 2D nanolayers. They have also shown that control over the morphology (from amorphous to 2D in-plane oriented layers to 3D out-of-plane oriented films) can be obtained by tuning the ALD temperature and plasma chemistry during plasma-enhanced ALD (Nanoscale 2018, Chem. Mater. 2019, ACS Appl. Mater. Interfaces 2020). In collaboration with colleagues from the Chemical Engineering department Bol’s team demonstrated that this is a big asset for tuning both the electronic (ACS Appl. Mater. Interfaces 2020) and electrocatalysis properties (ChemSusChem 2019) of 2D-TMDs. These contributions were heavily supported by HRTEM studies (Nanoscale 2018, Chem. Mater. 2019, ChemSusChem 2019) and DFT simulations (Chem. Mater. 2019, APL Mater. 2018, PCCP 2018) to understand the ALD growth mechanism and optimize the growth process.
Recently, the Bol group has demonstrated that the phase (e.g. TiS2 (metal) versus TiS3 (semiconductor)) of 2D nanolayers can be controlled during ALD by modulating the plasma chemistry (Chem. Mater. 2019). This sets the foundation for precise control of the electronic properties of 2D transition metal di/trichalcogenides by ALD. To fabricate high-performance electronic devices based on transition metal dichalcogenides, locally doped regions and control over the carrier density are essential. They demonstrated that they can locally grow p-doped TMDs with excellent control over the carrier density. In the approach the group developed, the carrier density of the semiconductor MoS2 can be tuned between 1017 cm-3 (insulator like) up to 1021 cm-3 (good conductor), covering the range of carrier densities needed for advanced nanoelectronic device concepts. (ACS Appl. Nano Mater. 2020)
Bol and her group have also shown that ALD makes it possible to grow TMDs selectively on one surface (in this case SiO2 ) while on another surface (Al2O3 ) the growth is inhibited. This was accomplished by using inhibitor molecules during the ALD process that selectively block nucleation in Al2O3. This can enable the integration of TMD layers in multilayer device stacks without the need for resist-based patterning of the delicate TMD layers. (ACS Mater. Lett. 2020).
International visibility, activities, prizes, scholarships etc.
Bol is a leader in the field of synthesis and integration of 1-D and 2-D nanomaterials for (future) nanoelectronics, photonics and sustainable energy applications. She creates and studies novel reliable, reproducible and scalable nanomaterial fabrication techniques, with precise control over the materials properties, which is essential for the realization of future nanomaterial applications. In her quest for new nanomaterial synthesis routes, she uses advanced characterization techniques and atomistic simulations to gain insights into the growth mechanisms of the nanomaterials. In her research she also tackles materials-related problems in the field of nanomaterial device integration. To turn novel nanomaterials into working devices, she develops new techniques to precisely pattern and integrate them with other device building blocks without deteriorating their properties.
In 2011 she moved to academia (TU/e), after 10 years of working in industry (Philips Research, the Netherlands, IBM TJ Watson Research Center, USA). At TU/e, Bol established two research lines. The first deals with the integration of carbon nanotubes and graphene with dielectrics and metals using ALD for nanoelectronic applications. Novel techniques based on selective ALD and plasma chemistry have been developed to make graphene and carbon nanotubes susceptible to ALD without deteriorating graphene’s properties. For this work, Bol received a prestigious NWO Vidi grant in 2012. In 2014 she received an ERC Consolidator grant, which gave her the opportunity to build up a new line of research on large-scale, controllable synthesis of 2D transition metal dichalcogenides using atomic layer deposition. The group uses advanced (in situ) characterization techniques and atomistic simulations to gain insight into the ALD reaction mechanisms. She is globally recognized as a pioneer in the field of ALD of 2D materials.
In 2019 she received an NWO Vici grant, which allowed her to further consolidate her research line on the synthesis of 2D TMDs. She has introduced defect engineering as a research theme and broadened the scope of this research line by including the investigation and optimization of the optical and catalytic properties of these nanomaterials.
Since 2011 Bol has supervised 11 PhD students and 8 Postdocs, of which several continued their career in academia, and others found positions in industrial R&D. Bol is holder of 20 US patents and has published over 90 peer-reviewed papers that have been cited over 8000 times.
At TU/e Bol has strongly contributed to improve diversity, equity and inclusion. She has been board member and chair of the Women in Science & Engineering Network at TU/e; she is a member of the TU/e diversity committee, which gives advice to the executive board of the university on how to stimulate diversity and gender equality at the university, and she is ‘Mentor for Women in Science’ in the department of Applied Physics.
5 key output/publications
Uniform Atomic Layer Deposition of Al2O3 on Graphene by Reversible Hydrogen Plasma Functionalization.
R.H.J. Vervuurt, B. Karasulu, M.A. Verheijen, W.M.M. Kessels, and A.A. Bol, Chemistry of Materials 29, 2090 (2017).
This work demonstrates our capabilities to form a graphene/Al2O3 hybrid structure using ALD without deteriorating the graphene electronic properties (no interface damage).
Low-temperature plasma-enhanced atomic layer deposition of 2-D MoS2: large area, thickness control and tuneable morphology.
A. Sharma, M.A. Verheijen, L. Wu, S. Karwal, V. Vandalon, H.C.M. Knoops, R. Sundaram, J.P. Hoffman, W.M. Kessels, and A.A. Bol, Nanoscale 10, 8615 (2018).
First demonstration of the synthesis of large-area 2D MoS2 by plasma-enhanced atomic layer deposition with precise thickness control.
Low temperature phase-controlled synthesis of titanium di- and tri-sulfide by atomic layer deposition.
S.B. Basuvalingam, Y. Zhang, M. Bloodgood, R. Godiksen, A. Curto, J.P. Hofmann, M.A. Verheijen, W.M.M. Kessels, and A.A. Bol, Chemistry of Materials 31, 9354 (2019).
Demonstrates for the first time that phase-controlled synthesis of di- and trisulfides is possible. Also, the first demonstration of the synthesis of a large area 2D transition metal trichalcogenide.
Probing the Origin and Suppression of Vertically Oriented Nanostructures of 2D WS2 Layers
S. Balasubramanyam, M.A. Bloodgood, M. Ommeren, T. Faraz, V. Vandalon, W.M.M. Kessels, M.A. Verheijen, and A.A. Bol, ACS Applied Materials & Interfaces 12, 3873-3885 (2020).
This paper provides mechanistic insight into atomic layer deposition of 2D transition metal dichalcogenides using advanced high resolution TEM studies to improve the ALD of 2D TMDs further.
Area-Selective Atomic Layer Deposition of Two-Dimensional WS 2 Nanolayers.
S. Balasubramanyam, M.J.M. Merkx, M.A. Verheijen, W.M.M. Kessels, A.J.M. Mackus, and A. A. Bol, ACS Materials Letters 2, 511-518 (2020).
First demonstration of area-selective deposition of a 2D transition metal dichalcogenide. This paper forms the foundation for the proposed area selective deposition in this proposal.