Chapter 4. Atomic Layer Deposition

Ritala, Mikko; Niinistö, Jaakko

doi:10.1039/9781847558794-00158

Cited by 49 publications

(63 citation statements)

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“…In general, two main reasons have been proposed to limit the growth rate in ALD: steric hindrance between the adsorbed precursor molecules, and limited number of reactive sites on the surface. [53] Relatively low growth rates have often been observed when using bulky metal thd precursors. For example, saturated growth rates of about 0.20 and 0.15 Å cycle −1 were reported using Ni(thd) 2 [60] and La(thd) 3 , [61] respectively, with H 2 S.…”

Section: Film Growth On Siliconmentioning

confidence: 99%

“…ALD offers large-area uniformity and precise control over film thickness, as well as unmatched conformality, i.e., uniform thickness over substrates with complex 3D shapes. [53][54][55] So far, ALD of MoS 2 has been reported using MoCl 5 with H 2 S, [43][44][45][46] as well as Mo(CO) 6 with H 2 S, [47,52] H 2 S plasma, [48] or dimethyl disulfide. [49][50][51] The films deposited with Mo(CO) 6 have mostly been amorphous due to the low deposition temperatures of 100-200 °C, [47,[49][50][51] although the films deposited with H 2 S plasma were polycrystalline.…”

Section: Introductionmentioning

confidence: 99%

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Atomic Layer Deposition of Crystalline MoS₂ Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Mattinen

Hatanpää

Sarnet

et al. 2017

Adv Materials Inter

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106

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Compared to the most well-known 2D material, graphene, which is a semi-metal, the semiconducting 2H phase of MoS 2 is advantageous in having a band gap suitable for electronic applications. In bulk form, MoS 2 has an indirect band gap of 1.3 eV, which increases as a function of decreasing film thickness. In monolayer MoS 2 (thickness ≈0.6 nm), the band gap becomes direct with a width of 1.8 eV. [1] Importantly, to meet the requirements of different applications, properties of MoS 2 and other TMDCs can be tuned by controlling the thickness, [1] doping and alloying, [5][6][7][8] surface modification and functionalization, [9][10][11] strain, [12,13] and by creating heterostructures with other 2D materials. [6,[14][15][16] The appealing properties of TMDCs have led to a wide range of proposed applications. MoS 2 has been extensively studied as a channel material in conventional field-effect transistors, [17][18][19][20][21] as well as phototransistors and other optoelectronic devices. [16,21,22] The 2D structure of TMDCs plays a crucial role in possible applications relying on more exotic quantum phenomena, such as valleytronics. [23,24] MoS 2 has also shown promise in, for example, catalysis, [25] batteries, [26] photovoltaics, [27] sensors, [28] and medicine. [29] The production of high-quality, large-area MoS 2 films with a thickness controllable down to a monolayer, as required in many of the aforementioned applications, still remains a major challenge. Additionally, in many cases, the processing temperature should be kept as low as possible in order to avoid damaging sensitive substrates, such as polymers or nanostructures. Initially, flakes of monolayer MoS 2 were produced from natural MoS 2 crystals using micromechanical exfoliation, a topdown method capable of producing high-quality monolayers, albeit with poor throughput as well as limited control over flake thickness and dimensions. [4,30,31] Liquid-phase exfoliation of bulk crystals, on the other hand, offers good scalability, but often suffers from limited flake size, poor crystallinity, or contamination. [4,31,32] Bottom-up methods offer a more controllable way to produce MoS 2 films. High-quality MoS 2 thin films are most commonly deposited by chemical vapor deposition (CVD) or sulfurization of metal or metal oxide thin films. The most common Molybdenum disulfide (MoS 2 ) is a semiconducting 2D material, which has evoked wide interest due to its unique properties. However, the lack of controlled and scalable methods for the production of MoS 2 films at low temperatures remains a major hindrance on its way to applications. In this work, atomic layer deposition (ALD) is used to deposit crystalline MoS 2 thin films at a relatively low temperature of 300 °C. A new molybdenum precursor, Mo(thd) 3 (thd = 2,2,6,6-tetramethylheptane-3,5-dionato), is synthesized, characterized, and used for film deposition with H 2 S as the sulfur precursor. Self-limiting growth with a low growth rate of ≈0.025 Å cycle −1 , straightforward thickness control, and large-area uni...

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Section: Film Growth On Siliconmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Atomic Layer Deposition of Crystalline MoS₂ Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Mattinen

Hatanpää

Sarnet

et al. 2017

Adv Materials Inter

Self Cite

106

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“…[39,40] The ALD thin film technique employed here is based on selflimiting surface-saturative reactions of alternately pulsed gaseous precursors. This unique deposition mechanism allows for the excellent thickness control for homogeneous and pinhole-free thin films deposited on high aspect ratio geometries [41,42]. Copper oxides (CuO and Cu2O) have previously been deposited on various surfaces and geometries via ALD using several copper precursor/oxygen source combinations [43,44,45,46].…”

Section: Introductionmentioning

confidence: 99%

Anomalous thickness-dependent optical energy gap of ALD-grown ultra-thin CuO films

Tripathi

Terasaki

Karppinen

2016

J. Phys.: Condens. Matter

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Usually an inverse square relation between the optical energy gap and the size of crystallites is observed for semiconducting materials due to the strong quantum localization effect. Coulomb attraction that may lead to a proportional dependence is often ignored or considered less important to the optical energy gap when the crystallite size or the thickness of a thin film changes. Here we report a proportional dependence between the optical energy gap and the thickness of ALD-grown CuO thin films due to a strong Coulomb attraction. The ultrathin films deposited in the thickness range of 9-81 nm show a p-type semiconducting behavior when analyzed by Seebeck coefficient and electrical resistivity measurements. The indirect optical energy gap nature of the films is verified from UV-vis spectrophotometric measurements. A progressive increase in the indirect optical energy gap from 1.06 to 1.24 eV is observed with the increase in the thickness of the films. The data are analyzed in the presence of Coulomb attractions using Brus model. The optical energy gap when plotted against the cubic root of the thickness of the films shows a linear dependence.

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“…The ALD processes were studied in more detail from both experimental and theoretical standpoints [12]. This is mainly due to the presence of simpler and clearer concepts concerning the chemical reactions occurring on the substrate during the ALD process [13] as compared with MOCVD [14,15].…”

Section: Introductionmentioning

confidence: 99%

Features of oxide layer formation in high-aspect slot structures by means of MOCVD

Shevtsov

Kuchumov

Кручинин

et al. 2015

Journal of Crystal Growth

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Chapter 4. Atomic Layer Deposition

Cited by 49 publications

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Atomic Layer Deposition of Crystalline MoS₂ Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Atomic Layer Deposition of Crystalline MoS₂ Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Anomalous thickness-dependent optical energy gap of ALD-grown ultra-thin CuO films

Features of oxide layer formation in high-aspect slot structures by means of MOCVD

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Chapter 4. Atomic Layer Deposition

Cited by 49 publications

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Atomic Layer Deposition of Crystalline MoS2 Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Atomic Layer Deposition of Crystalline MoS2 Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Anomalous thickness-dependent optical energy gap of ALD-grown ultra-thin CuO films

Features of oxide layer formation in high-aspect slot structures by means of MOCVD

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Atomic Layer Deposition of Crystalline MoS₂ Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth

Atomic Layer Deposition of Crystalline MoS₂ Thin Films: New Molybdenum Precursor for Low‐Temperature Film Growth