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[Display omitted] • Atomic layer deposition can smooth surface roughness. • Root-mean-square roughness reduced versus atomic layer deposition. • Lateral spacing between surface asperities increased versus atomic layer deposition. • Smoothing surface roughness improved reflectivity of silver mirrors. Al 2 O 3 atomic layer deposition (ALD) was used to smooth the roughness on silicon wafers obtained prior to chemical mechanical polishing (CMP). The initial silicon wafers had an average RMS surface roughness of 3.3 nm as determined by atomic force microscopy (AFM) measurements. AFM line scans also measured an average lateral spacing of ≈490 nm between the surface asperities. The RMS roughness decreased and the average lateral spacing increased progressively with number of Al 2 O 3 ALD cycles. After 3000 Al 2 O 3 ALD cycles that deposit an Al 2 O 3 film thickness of 370 nm, the RMS roughness reduced to 1.5 nm and the average lateral spacing between the surface asperities increased to ≈890 nm. Additional Al 2 O 3 ALD cycles produced little change in the RMS roughness or average lateral spacing. The efficiency of the smoothing decreased when the lateral distance between the surface asperities was much larger than the Al 2 O 3 ALD film thickness. Power spectral density (PSD) analysis revealed that the ALD smoothing was most effective for surface topographical features with lateral spacings in the range of 10s to 100s of nanometers. Reflectivity studies of silver films deposited on the silicon wafers also demonstrated that Al 2 O 3 ALD smoothing improved the optical performance of reflective mirrors. [ABSTRACT FROM AUTHOR]

The recent advancement of semiconductor devices to the near-atomic scale necessitated the development of atomic layer processing methods, including molecular layer deposition (MLD). This gas-phase deposition technique creates semipermeable polymer films with precise control of composition and thickness. Herein, MLD was used to produce thin-film composite reverse osmosis membranes. Aromatic polyamide films as thin as 0.5 nm were applied to NF270 nanofiltration membranes using m -phenylenediamine and trimesoyl chloride. Within two molecular layers, desalination performance was affected. As film thickness increased to 15 nm (48 MLD cycles), performance progressed from nanofiltration to reverse osmosis metrics in terms of salt rejection and water permeance. With film thickness > 5 nm, rejection values exceeded a small sampling of commercial membranes. In all cases, a tradeoff between rejection and permeance was observed. Atomic force microscopy measurements indicate that MLD enhancement led to removal of small-scale roughness features and resulted in a root mean square roughness difference of <0.1 nm from the substrate. These initial MLD studies represent a novel processing approach that offers a potential pathway for the fabrication of membranes with finely tailored properties. [Display omitted] • MLD added an ultrathin MPD-TMC polyamide active layer to commercial NF membranes. • Progressive MLD systematically altered flux/rejection metrics from NF to RO values. • Controlled increase of MLD layer thickness increased rejection but decreased flux. • Atomic force microscopy revealed that MLD removed small-scale roughness features. [ABSTRACT FROM AUTHOR]

The recent advancement of semiconductor devices to the near-atomic scale necessitated the development of atomic layer processing methods, including molecular layer deposition (MLD). This gas-phase deposition technique creates semipermeable polymer films with precise control of composition and thickness. Herein, MLD was used to produce thin-film composite reverse osmosis membranes. Aromatic polyamide films as thin as 0.5 nm were applied to NF270 nanofiltration membranes using m -phenylenediamine and trimesoyl chloride. Within two molecular layers, desalination performance was affected. As film thickness increased to 15 nm (48 MLD cycles), performance progressed from nanofiltration to reverse osmosis metrics in terms of salt rejection and water permeance. With film thickness > 5 nm, rejection values exceeded a small sampling of commercial membranes. In all cases, a tradeoff between rejection and permeance was observed. Atomic force microscopy measurements indicate that MLD enhancement led to removal of small-scale roughness features and resulted in a root mean square roughness difference of <0.1 nm from the substrate. These initial MLD studies represent a novel processing approach that offers a potential pathway for the fabrication of membranes with finely tailored properties. [Display omitted] • MLD added an ultrathin MPD-TMC polyamide active layer to commercial NF membranes. • Progressive MLD systematically altered flux/rejection metrics from NF to RO values. • Controlled increase of MLD layer thickness increased rejection but decreased flux. • Atomic force microscopy revealed that MLD removed small-scale roughness features. [ABSTRACT FROM AUTHOR]