Atomic Layer Deposition of Gallium Sulfide Films Using Hexakis(dimethylamido)digallium and Hydrogen Sulfide

Abstract

Gallium sulfide (GaS x ) was synthesized for the first time via atomic layer deposition (ALD), using hexakis(dimethylamido)digallium and hydrogen sulfide. The growth characteristics and surface reaction mechanism for the GaS x ALD were investigated using in situ quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy measurements. The as-deposited films were analyzed for their surface morphology, elemental stoichiometry, chemical states and stability, and crystallinity, using a variety of characterization techniques. These measurements revealed that the GaS x growth was self-limiting in the temperature range of 125–225 °C and the growth per cycle decreased linearly with increasing temperature, from ∼1.0 Å/cycle at 125 °C to ∼0.5 Å/cycle at 225 °C. The S/Ga ratio was between 1.0 and 1.2 in the temperature range of 125–200 °C, but decreased to 0.75 at 225 °C. The GaS x films were amorphous and the refractive index increased from ∼1.8 to 2.5 with increasing temperature. Significantly, electrochemical testing showed that the ALD GaS x is a promising lithium-ion battery (LIB) anode material, exhibiting reliable cyclability and a high specific capacity of 770 mAh/g at a current density of 320 mA/g in the voltage window of 0.01–2.00 V.

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

“…For many ALD oxide processes, hydroxyl (OH) groups are the major reactive sites, [62] whereas the analogous thiol (SH) groups can play an important role for sulfides. As an example, Meng et al [63] found a rapid decrease in the density of thiol groups, and, consequently, in the ALD growth rate of GaS x deposited from Ga 2 (NMe 2 ) 6 and H 2 S, when increasing the deposition temperature from 125 to 225 °C.…”

Intramolecularly Coordinated Gallium Sulfides: Suitable Single Source Precursors for GaS Thin Films

“…It was previouslys hown that the presence of gallium is crucial for the sufficient solubility of raree arth ions in amorphous chalcogenides, which is generally low in typical binary compositions (As/S, As/Se, Ge/S, Ge/Se,e tc.). [9] Recently,G aS x films were prepared by atomic layer deposition (ALD) by using Ga 2 (NMe 2 ) 6 and H 2 S. [10] In addition, synthesis of nanoparticles, [11] nanotubes, [12] or flowerlike structures [13] of GaS and Ga 2 S 3 have also been reported. [3] Thereafter,H ampden-Smith et al also reported the preparation of crystalline a-Ga 2 S 3 films by aerosol-assisted CVD from Ga(S 2 CMe) 2 Me(dmpy) or Ga(S 2 CMe) 3 (dmpy) (dmpy = 3,5-dimethylpyridine) [4] and finally, O'Brien et al described using Ga(S 2 CNMeHex) 3 to deposit a-Ga 2 S 3 films on GaAs(111)s ubstrates by low-pressure CVD [5] and ad ifferent single-source precursor (SSP), [Ga(SiPr) 2 (m-SiPr)] 2 , was used for the preparationo fh igh-quality a-Ga 2 S 3 and g-Ga 2 S 3 films by the CVD method as well.…”

Nanoengineering Energy Conversion and Storage Devices via Atomic Layer Deposition

“…The short ion diffusion length facilitates the diffusion and the corresponding insertion and extraction of the ions. The active materials fabricated by ALD mainly include metal oxides (e.g., SnO 2 , ZnO, TiO 2 , V 2 O 5 , Co 3 O 4 , Fe 2 O 3 , NiO, MnO x , RuO 2 ), [179][180][181][182][183][184][185][186][187] sulphides (e.g., GaS x ), [188,189] and others (e.g., LiCoO 2 , LiMn 2 O 4 , Li 4 Ti 5 O 12 , FePO 4 , LiFePO 4 ). [178] The short path lengths for ion diffusion permit the application of low Li + conductive materials, high rate performance and high energy densities.…”