Browsing by Author "Mentel, Kamila K."

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Area-Selective Atomic Layer Deposition on Functionalized Graphene Prepared by Reversible Laser Oxidation
(2022-10-13) Mentel, Kamila K.; Emelianov, Aleksei V.; Philip, Anish; Johansson, Andreas; Karppinen, Maarit; Pettersson, Mika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Area-selective atomic layer deposition (ALD) is a promising “bottom-up” alternative to current nanopatterning techniques. While it has been successfully implemented in traditional microelectronic processes, selective nucleation of ALD on 2D materials has so far remained an unsolved challenge. In this article, a precise control of the selective deposition of ZnO on graphene at low temperatures (<250 °C) is demonstrated. Maskless femtosecond laser writing is used to locally activate predefined surface areas (down to 300 nm) by functionalizing graphene to achieve excellent ALD selectivity (up to 100%) in these regions for 6-nm-thick ZnO films. The intrinsic conductive properties of graphene can be restored by thermal annealing at low temperature (300 °C) without destroying the deposited ZnO patterns. As the graphene layer can be transferred onto other material surfaces, the present patterning technique opens new attractive ways for various applications in which the functionalized graphene is utilized as a template layer for selective deposition of desired materials.
Deterministic Modification of CVD Grown Monolayer MoS2 with Optical Pulses
(2021-05-21) Turunen, Mikko T.; Hulkko, Eero; Mentel, Kamila K.; Bai, Xueyin; Akkanen, Suvi Tuuli; Amini, Mohammad; Li, Shisheng; Lipsanen, Harri; Pettersson, Mika; Sun, Zhipei
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Transition metal dichalcogenide monolayers have demonstrated a number of exquisite optical and electrical properties. Here, the authors report the optical modification of topographical and optical properties of monolayer MoS2 with femtosecond pulses under an inert atmosphere. A formation of three-dimensional structures on monolayer MoS2 with tunable height up to ≈20 nm is demonstrated. In contrast to unmodified monolayer MoS2, these optically modified structures show significantly different optical properties, such as lower photoluminescence intensity and longer fluorescence lifetime. The results suggest a novel way to modify transition metal dichalcogenide materials for mechanic, electronic and photonic applications.
Enhanced Nonlinear Optical Responses in MoS2 via Femtosecond Laser-Induced Defect-Engineering
(2024-11-12) Akkanen, Suvi-Tuuli; Arias Muñoz, Juan Camilo; Emelianov, Aleksei V.; Mentel, Kamila K.; Tammela, Juhani; Partanen, Mikko; Das, Susobhan; Pettersson, Mika; Sun, Zhipei
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
2D materials are a promising platform for applications in many fields as they possess a plethora of useful properties that can be further optimized by careful engineering, for example, by defect introduction. While reliable high-yield defect engineering methods are in demand, most current technologies are expensive, harsh, or non-deterministic. Optical modification methods offer a cost-effective and fast mechanism to engineer the properties of 2D materials at any step of the device fabrication process. In this paper, the nonlinear optical responses of mono-, bi-, and trilayer molybdenum disulfide (MoS2) flakes are enhanced by deterministic defect-engineering with a femtosecond laser. A 50-fold enhancement in the third harmonic generation (THG) and a 3.3-fold increase in the second harmonic generation (SHG) in the optically modified areas is observed. The enhancement is attributed to resonant SHG and THG processes arising from optically introduced mid-band gap defect states. These results demonstrate a highly controllable, sub-micrometer resolution tool for enhancing the nonlinear optical responses in 2D materials, paving the way for prospective future applications in optoelectronics, quantum technologies, and energy solutions.