Surface Smoothing by Atomic Layer Deposition and Etching for the Fabrication of Nanodevices.

In many nano(opto)electronic devices, the roughness at surfaces and interfaces is of increasing importance, with roughness often contributing toward losses and defects, which can lead to device failure. Consequently, approaches that either limit roughness or smoothen surfaces are required to minimize surface roughness during fabrication. The atomic-scale processing techniques atomic layer deposition (ALD) and atomic layer etching (ALE) have experimentally been shown to smoothen surfaces, with the added benefit of offering uniform and conformal processing and precise thickness control.

Surface Chemistry during Atomic Layer Deposition of Pt Studied with Vibrational Sum-Frequency Generation.

A detailed understanding of the growth of noble metals by atomic layer deposition (ALD) is key for various applications of these materials in catalysis and nanoelectronics. The Pt ALD process using MeCpPtMe and O gas as reactants serves as a model system for the ALD processes of noble metals in general. The surface chemistry of this process was studied by vibrational broadband sum-frequency generation (BB-SFG) spectroscopy, and the results are placed in the context of a literature overview of the reaction mechanism.

Atmospheric-Pressure Plasma-Enhanced Spatial ALD of SiO Studied by Gas-Phase Infrared and Optical Emission Spectroscopy.

An atmospheric-pressure plasma-enhanced spatial atomic layer deposition (PE-s-ALD) process for SiO using bisdiethylaminosilane (BDEAS, SiH[NEt]) and O plasma is reported along with an investigation of its underlying growth mechanism. Within the temperature range of 100-250 °C, the process demonstrates self-limiting growth with a growth per cycle (GPC) between 0.12 and 0.

Atomic insights into the oxygen incorporation in atomic layer deposited conductive nitrides and its mitigation by energetic ions.

Oxygen is often detected as impurity in metal and metal nitride films prepared by atomic layer deposition (ALD) and its presence has profound and adverse effects on the material properties. In this work, we present the case study of HfN films prepared by plasma-assisted ALD by alternating exposures of CpHf(NMe) and H plasma. First, we identify the primary source of O contamination in the film.

Atomic Layer Deposition of Al-Doped MoS: Synthesizing a p-type 2D Semiconductor with Tunable Carrier Density.

Extrinsically doped two-dimensional (2D) semiconductors are essential for the fabrication of high-performance nanoelectronics among many other applications. Herein, we present a facile synthesis method for Al-doped MoS via plasma-enhanced atomic layer deposition (ALD), resulting in a particularly sought-after -type 2D material. Precise and accurate control over the carrier concentration was achieved over a wide range (10 up to 10 cm) while retaining good crystallinity, mobility, and stoichiometry.

Large area, patterned growth of 2D MoS and lateral MoS-WS heterostructures for nano- and opto-electronic applications.

The patterned growth of transition metal dichalcogenides (TMDs) and their lateral heterostructures is paramount for the fabrication of application-oriented electronics and optoelectronics devices. However, the large scale patterned growth of TMDs remains challenging. Here, we demonstrate the synthesis of patterned polycrystalline 2D MoS thin films on device ready SiO/Si substrates, eliminating any etching and transfer steps using a combination of plasma enhanced atomic layer deposition (PEALD) and thermal sulfurization.

Probing the Origin and Suppression of Vertically Oriented Nanostructures of 2D WS Layers.

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) such as WS are promising materials for nanoelectronic applications. However, growth of the desired horizontal basal-plane oriented 2D TMD layers is often accompanied by the growth of vertical nanostructures that can hinder charge transport and, consequently, hamper device application. In this work, we discuss both the formation and suppression of vertical nanostructures during plasma-enhanced atomic layer deposition (PEALD) of WS.

Polarized Raman spectroscopy to elucidate the texture of synthesized MoS.

Texture has a significant impact on several key properties of transition-metal dichalcogenides (TMDs) films. Films with in-plane oriented grains have been successfully implemented in nano- and opto-electronic devices, whereas, films with out-of-plane oriented material have shown excellent performance in catalytic applications. It will be demonstrated that the texture of nanocrystalline TMD films can be determined with polarized Raman spectroscopy.

Edge-Site Nanoengineering of WS by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution.

Edge-enriched transition metal dichalcogenides, such as WS, are promising electrocatalysts for sustainable production of H through the electrochemical hydrogen evolution reaction (HER). The reliable and controlled growth of such edge-enriched electrocatalysts at low temperatures has, however, remained elusive. In this work, we demonstrate how plasma-enhanced atomic layer deposition (PEALD) can be used as a new approach to nanoengineer and enhance the HER performance of WS by maximizing the density of reactive edge sites at a low temperature of 300 °C.

Chemical Analysis of the Interface between Hybrid Organic-Inorganic Perovskite and Atomic Layer Deposited AlO.

Ultrathin metal oxides prepared by atomic layer deposition (ALD) have gained utmost attention as moisture and thermal stress barrier layers in perovskite solar cells (PSCs). We have recently shown that 10 cycles of ALD AlO deposited directly on top of the CHNHPbICl perovskite material, are effective in delivering a superior PSC performance with 18% efficiency (compared to 15% of the AlO-free cell) with a long-term humidity-stability of more than 60 days. Motivated by these results, the present contribution focuses on the chemical modification which the CHNHPbICl perovskite undergoes upon growth of ALD AlO.

Low-temperature plasma-enhanced atomic layer deposition of 2-D MoS: large area, thickness control and tuneable morphology.

Low-temperature controllable synthesis of monolayer-to-multilayer thick MoS2 with tuneable morphology is demonstrated by using plasma enhanced atomic layer deposition (PEALD). The characteristic self-limiting ALD growth with a growth-per-cycle of 0.1 nm per cycle and digital thickness control down to a monolayer are observed with excellent wafer scale uniformity.

Simultaneous scanning tunneling microscopy and synchrotron X-ray measurements in a gas environment.

A combined X-ray and scanning tunneling microscopy (STM) instrument is presented that enables the local detection of X-ray absorption on surfaces in a gas environment. To suppress the collection of ion currents generated in the gas phase, coaxially shielded STM tips were used. The conductive outer shield of the coaxial tips can be biased to deflect ions away from the tip core.

Influence of surface temperature on the mechanism of atomic layer deposition of aluminum oxide using an oxygen plasma and ozone.

We have examined the role of substrate temperature on the surface reaction mechanisms during the atomic layer deposition (ALD) of Al(2)O(3) from trimethyl aluminum (TMA) in combination with an O(2) plasma and O(3) over a substrate temperature range of 70-200 °C. The ligand-exchange reactions were investigated using in situ attenuated total reflection Fourier transform infrared spectroscopy. Consistent with our previous work on ALD of Al(2)O(3) from an O(2) plasma and O(3) [Rai, V.

Surface reaction mechanisms during ozone and oxygen plasma assisted atomic layer deposition of aluminum oxide.

We have elucidated the reaction mechanism and the role of the reactive intermediates in the atomic layer deposition (ALD) of aluminum oxide from trimethyl aluminum in conjunction with O(3) and an O(2) plasma. In situ attenuated total reflection Fourier transform infrared spectroscopy data show that both -OH groups and carbonates are formed on the surface during the oxidation cycle. These carbonates, once formed on the surface, are stable to prolonged O(3) exposure in the same cycle.