Surface chemical reactions during atomic layer deposition of ZnO, ZnS, and Zn(O,S)

Van, Tran Thi Ngoc; Ansari, Abu Saad; Shong, Bonggeun

doi:10.1116/1.5079247

Cited by 16 publications

(7 citation statements)

References 52 publications

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“…Because ALD reactions known to occur near room temperature (e.g., those of Al 2 O 3 or ZnO) exhibited activation energy values of ca. 1 eV by DFT calculations using a similar method as the current study, , the ALD of SnN x would also proceed at low temperatures. On the contrary, as temperature increases, the molecular adsorption of TDMASn becomes less favorable, such that Δ G becomes >0 above ca.…”

Section: Resultsmentioning

confidence: 59%

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Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Ansari

Nandi

Janíček

et al. 2019

ACS Appl. Mater. Interfaces

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We present an atomic layer deposition (ALD) process for the synthesis of tin nitride (SnN x ) thin films using tetrakis(dimethylamino) tin (TDMASn, Sn(NMe2)4) and ammonia (NH3) as the precursors at low deposition temperatures (70–200 °C). This newly developed ALD scheme exhibits ideal ALD features such as self-limited film growth at 150 °C. The growth per cycle (GPC) was found to be ∼0.21 nm/cycle at 70 °C, which decreased with increasing deposition temperature. Interestingly, when the deposition temperature was between 125 and 180 °C, the GPC remained almost constant at ∼0.10 nm/cycle, which suggests an ALD temperature window, whereas upon further increasing the temperature to 200 °C, the GPC considerably decreased to ∼0.04 nm/cycle. Thermodynamic analysis via density functional theory calculations showed that the self-saturation of TDMASn would occur on an NH2-terminated surface. Moreover, it also suggests that the condensation of a molecular precursor and the desorption of surface *NH2 moieties would occur at lower and higher temperatures outside the ALD window, respectively. Thanks to the characteristics of ALD, this process could be used to conformally and uniformly deposit SnN x onto an ultranarrow dual-trench Si structure (minimum width: 15 nm; aspect ratio: ∼6.3) with ∼100% step coverage. Several analysis tools such as transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and secondary-ion mass spectrometry were used to characterize the film properties under different deposition conditions. XRD showed that a hexagonal SnN phase was obtained at a relatively low deposition temperature (100–150 °C), whereas cubic Sn3N4 was formed at a higher deposition temperature (175–200 °C). The stoichiometry of these thermally grown ALD-SnN x films (Sn-to-N ratio) deposited at 150 °C was determined to be ∼1:0.93 with negligible impurities. The optoelectronic properties of the SnN x films, such as the band gap, wavelength-dependent refractive index, extinction coefficient, carrier concentration, and mobility, were further evaluated via spectroscopic ellipsometry analysis. Finally, ALD-SnN x -coated Ni-foam (NF) and hollow carbon nanofibers were successfully used as free-standing electrodes in electrochemical supercapacitors and in Li-ion batteries, which showed a higher charge-storage time (about eight times greater than that of the uncoated NF) and a specific capacity of ∼520 mAh/g after 100 cycles at 0.1 A/g, respectively. This enhanced performance might be due to the uniform coverage of these substrates by ALD-SnN x , which ensures good electric contact and mechanical stability during electrochemical reactions.

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Section: Resultsmentioning

confidence: 59%

“…(a) Full survey XPS spectra of the ALD-grown SnN x film at 150 °C and the corresponding high-resolution spectra of (b) Sn 3d and (c) N 1s. Orange lines indicate reported positions/values for respective types of chemical bonds. − …”

Section: Resultsmentioning

confidence: 99%

Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Ansari

Nandi

Janíček

et al. 2019

ACS Appl. Mater. Interfaces

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“…The larger growth rates on the TiN substrate may have originated from the 3D growth, as reflected in the large surface roughness on the TiN substrate [root-mean-squared (RMS) roughness of 5.78 nm, Figure S1, Supporting Information (SI)] compared with the low roughness on the SiO 2 substrate (RMS roughness of 1.1 nm, Figure S1, SI). The different surface morphology indicates Stranski–Krastanov-type growth on SiO 2 and Volmer–Weber-type island growth on the TiN substrate, possibly due to the uniformly high concentration of the OH group on SiO 2 , as opposed to its nonuniform, sparse distribution on TiN. − (The initial surface roughness of the TiN substrate was quite low; RMS roughness: 0.5 nm.) Previous study also suggested that agglomeration of initial clusters could induce the substrate-dependent morphology of ALD films .…”

Section: Resultsmentioning

confidence: 99%

Atomic Layer Deposition of Nanocrystalline-As-Deposited (GeTe)_x(Sb₂Te₃)_1–x Films for Endurable Phase Change Memory

et al. 2019

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This paper introduces a new atomic layer deposition process for highly conformal, nanocrystalline-as-deposited GeTe–Sb2Te3 pseudobinary film growth at a deposition temperature of 130 °C. The process utilizes Ge(II)-amidoguanidinate (GeIIN(CH3)2[(N i Pr)2CN(CH3)2]), Te(Si(CH3)3)2, and Sb(OC2H5)3 with an NH3 coreagent. The alternative GeTe and Sb2Te3 subcycles produced various film compositions, all consistent with the GeTe–Sb2Te3 tie lines, owing to the stoichiometric reactions between the precursors without involvement of undesirable side reactions. The density of the nanocrystalline Ge2Sb2Te5 (GST225) films was 6.2 g·cm–3, similar to the density of the bulk crystalline material. The crystallization behaviors indicated that the distribution of the constituent elements of the GST225 films was highly uniform at the atomic level, as opposed to the case of the low-temperature (100 °C)-deposited films. The cubic to hexagonal transition at 350 °C upon postannealing produced (0001) hexagonal planes highly aligned along the substrate. The demonstration of the phase change memory device achieved high cycling endurance (>107). Considering that further scaling and optimization of the cell design can improve the electrical performance, the nanocrystalline GST films introduced herein can provide potential utilities in the large-capacity three-dimensional vertical-type phase change memory.

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“…Therefore, the potential energy diagrams of the DEZ precursor reacting with an OH-terminated Si surface (Figure e) and graphitic C surfaces with some common types of defects (Figure f) were compared. The reactions of the DEZ precursor with the surfaces are assumed to be the following (* denotes surface adsorption sites): The proton transfer/ligand exchange reaction occurs on OH-terminated Si, and the dissociative adsorption of DEZ into C 2 H 5 and Zn(C 2 H 5 ) moieties occurs on the carbonaceous surface. − While the adsorption of Zn by DEZ on the *OH surface was confirmed to be facile in terms of both activation energy ( E a ) and reaction energy (Δ E ), the carbon-based substrate is expected to show a much lower reactivity, with E a values greater than 150 kJ/mol, regardless of the type of defect. In particular, a graphitic surface without defects (PG) exhibits a large endothermicity upon the dissociative adsorption of DEZ in contrast to adsorption on defective graphitic sites, which is exothermic.…”

Section: Resultsmentioning

confidence: 99%

Thermal Annealing of Molecular Layer-Deposited Indicone Toward Area-Selective Atomic Layer Deposition

Lee

Baek

Kim

et al. 2020

ACS Appl. Mater. Interfaces

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Area-selective atomic layer deposition (AS-ALD) is a promising technique for fine nanoscale patterning, which may overcome the drawbacks of conventional top-down approaches for the fabrication of future electronic devices. However, conventional materials and processes often employed for AS-ALD are inadequate for conformal and rapid processing. We introduce a new strategy for AS-ALD based on molecular layer deposition (MLD) that is compatible with large-scale manufacturing. Conformal thin films of "indicone" (indium alkoxide polymer) are fabricated by MLD using INCA-1 (bis(trimethylsily)amidodiethylindium) and HQ (hydroquinone). Then, the MLD indicone films are annealed by a thermal heat treatment under vacuum. The properties of the indicone thin films with different annealing temperatures were measured with multiple optical, physical, and chemical techniques. Interestingly, a nearly complete removal of indium from the film was observed upon annealing to ca. 450 °C and above. The chemical mechanism of the thermal transformation of the indicone film was investigated by density functional theory calculations. Then, the annealed indicone thin films were applied as an inhibiting layer for the subsequent ALD of ZnO, where the deposition of approximately 20 ALD cycles (equivalent to a thickness of approximately 4 nm) of ZnO was successfully inhibited. Finally, patterns of annealed MLD indicone/Si substrates were created on which the area-selective deposition of ZnO was demonstrated.

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Surface chemical reactions during atomic layer deposition of ZnO, ZnS, and Zn(O,S)

Cited by 16 publications

References 52 publications

Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Atomic Layer Deposition of Nanocrystalline-As-Deposited (GeTe)_x(Sb₂Te₃)_1–x Films for Endurable Phase Change Memory

Thermal Annealing of Molecular Layer-Deposited Indicone Toward Area-Selective Atomic Layer Deposition

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Surface chemical reactions during atomic layer deposition of ZnO, ZnS, and Zn(O,S)

Cited by 16 publications

References 52 publications

Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Atomic Layer Deposition of Nanocrystalline-As-Deposited (GeTe)x(Sb2Te3)1–x Films for Endurable Phase Change Memory

Thermal Annealing of Molecular Layer-Deposited Indicone Toward Area-Selective Atomic Layer Deposition

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Atomic Layer Deposition of Nanocrystalline-As-Deposited (GeTe)_x(Sb₂Te₃)_1–x Films for Endurable Phase Change Memory