PhD Position | TMDC materials: tuning transport properties by substitutional doping and phase transition

29 Mar 2024
Job Information

Organisation/Company

IMEC

Research Field

All

Researcher Profile

First Stage Researcher (R1)

Country

Belgium

Application Deadline

15 Apr 2024 - 23:59 (Europe/Brussels)

Type of Contract

Temporary

Job Status

Full-time

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

be involved in state-of-the-art 2D research, and contribute to set-up the world’s first 2D experimental pilot line - benefit from imec’s extensive know-how on material processing for nanoelectronics applications

Apply 

2D layered Transition Metal Di-Chalcogenides (TMDCs) are envisioned for replacing silicon in advanced CMOS logic technology nodes, in the form of stacked nanosheet heterostructures. The nanofabrication of such devices, using VLSI compliant processing technology, represents a tremendous challenge for the community. Logic systems require to build NMOS and PMOS transistors, using the same starting channel material; this is done by creating, artificially, additional negative charges (electrons) or positive charges (holes) in the semiconducting material – this is called doping. In silicon this is done by implanting donor or acceptor elements using a high energetic beam, followed by an annealing to fix/stabilize the dopants in the crystalline structure.

 

Although doping of bulk silicon is well understood, the doping of an intrinsically 2D layer, with a thickness of only a few Angströms, represent immense difficulties. This is even more challenging in a stacked nanosheet configuration, where multiple stacked TMDC layers need to be doped simultaneously. In the last few years, extrinsic doping by surface charge transfer (gas adsorption, self-assembled organic molecules, metal oxide) was explored and demonstrated some doping effect, however these methods are unstable with time and temperature, difficult to control and/or impossible to integrate within a CMOS process flow. Substitutional doping, i.e. the replacement of metal atoms (cations) or chalcogen atoms (anions) by donor or acceptor elements, does not, a priori, suffer from these problems. In addition, structural change of the crystalline structure of the 2D layer (2H to 1T phase transition) could also be considered to induce more severe conductivity changes, particularly suitable for contact formation (locally turning the TMDC layer from semiconductor to metallic).

 

The PhD topic described here will address the challenge of controlled  substitutional doping and controlled  TMDC phase transitions. The work will rely on three different approaches. First, anion substitutional doping will be explored by developing a downstream plasma-based approach for creating controlled chalcogen vacancies, subsequently filled by group VII or group V atoms for n-type and p-type doping respectively. Second, doping using low energy phosphorus implantation will be studied, controlling the implantation depth by means of sacrificial polymer films. As a third approach, plasma-induced 2H-1T phase transitions will be explored using soft conditions (pulsed plasma discharges) leading to controlled crystallinity changes possibly combined with chemical doping. The effect of capping layers(s) on this structural transition will also be part of the research activity.

 

As a PhD student, you will learn to work in a highly dynamic and multicultural environment and be exposed to a large variety of analytical techniques and experimental methods. You will use VLSI-compliant downstream plasma systems as well as laboratory scale flexible platforms. You will learn micro/nano-fabrication methods and run them by yourself or use imec’s pilot line and/or infrastructure at the KULeuven. You will learn how to measure transport properties (carrier density, mobility, Ion/Ioff ratio…) on samples that you will fabricate yourself. Surface chemistry and physics will be studied both ex situ and post operando by x-ray photoelectron spectroscopy (XPS), Secondary ion mass spectroscopy (SIMS) and high-resolution angle-resolved photoemission spectroscopy (ARPES). Other complementary physical characterization techniques like elastic recoil detection analysis (ERDA), atomic force microscopy (AFM), scanning and transmission electron microscopy (SEM, TEM) and low-energy ion scattering will be made available to support your mechanistic studies.

 

At imec, we have a large expert team with various backgrounds in materials and deposition techniques, state of the art 200mm and 300mm process lines, laboratories, device learning and modelling. The PhD candidate will be part of the Unit Process Module department at imec, with strong links to the Material Engineering department of KU Leuven.

Type of work: 40% experimental, 30% characterization, 20% data analysis, 10% literature study and writing

Supervisor: Clement Merckling

Co-supervisor: Alexis Franquet

Daily advisor: Jean-Francois de Marneffe, Rita Tilmann

The reference code for this position is 2024-023. Mention this reference code on your application form.

Find all the information on doing a PhD at imec, as well as all required documents for your application file, here: Imec - PhD at imec (Belgium) (imec-int.com)

Requirements

Research Field

Engineering

Education Level

Master Degree or equivalent

Research Field

Other

Education Level

Master Degree or equivalent

Skills/Qualifications

Required background: Master in engineering technology / Master in engineering science / Master in materials science / Master in science

Languages

ENGLISH

Level

Excellent

Additional Information
Selection process

• Read the PhD Admission Requirements
• Choose your topics and look up the reference codes (2023-001). You can apply for maximum 3 projects in total.
• Collect your documents in pdf format:
  • Download and complete the motivation letter
  • Resume
  • Bachelor's degree and transcripts
  • Master's degree and transcripts
    If you have not finished your master program yet, you can submit your degree when you graduate. Do submit your master examination results available at the time of application.
  • Proof of your English language proficiency (refer to the PhD Admission Requirements  for details)
  • GRE score (refer to the PhD Admission Requirements  for details)
  • Ask two referees to fill out the evaluation form  for you and have them send their input to [email protected]  before the deadline (15 April 2023 or 15 December 2023). The letters of recommendation are confidential and are an essential part of your application. We will not be able to process your application without the evaluation forms so it is important that you contact your referees in time.

Additional comments
General information

There are two application windows:

• From 15 March until 15 April
• From 15 October until 15 December

Imec itself is not giving PhD degrees but acts as a host research institute for PhD and postdoc research in collaboration with 5 Flemish universities: KU Leuven, UGent, VUBrussel, UAntwerpen, UHasselt. Imec has also signed dual degree PhD agreements with Flemish and international universities. Both engineers and scientists can apply because of the multidisciplinary character of our research. PhDs get supported by professors of both national and international universities, all of them experts in their domains.
Imec has a dual degree agreement with different universities.

If you have more questions after reading the information below, contact [email protected] .

Website for additional job details

https://www.imec-int.com/en/work-at-imec/job-opportunities/phd-at-imec

Work Location(s)

Number of offers available

1

Company/Institute

imec

Country

Belgium

Geofield

Where to apply

Website

https://www.imec-int.com/en/work-at-imec/job-opportunities/tmdc-materials-tunin…

Contact

City

Leuven

Website

http://www.imec-int.com

Street

Kapeldreef 75

Postal Code

3001

E-Mail

[email protected]

STATUS: EXPIRED