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Oxygen evolution reaction driven by NiO microflowers.

The low efficiency of water electrolysis mostly arises from the thermodynamic uphill oxygen evolution reaction. The efficiency can be greatly improved by rationally designing low-cost and efficient oxygen evolution anode materials. Herein, we report the synthesis of Ni–P alloys adopting a facile electroless plating method under mild conditions on nickel substrates. The relationship between the Ni–P properties and catalytic activity allowed us to define the best conditions for the electroless synthesis of highperformance Ni–P catalysts. Indeed, the electrochemical investigations indicated an increased catalytic response by reducing the thickness and Ni/P ratio in the alloy. Furthermore, the Ni–P catalysts with optimized size and composition deposited on Ni foam exposed more active sites for the oxygen evolution reaction, yielding a current density of 10 mA cm−2 at an overpotential as low as 335 mV, exhibiting charge transfer resistances of only a few ohms and a remarkable turnover frequency (TOF) value of 0.62 s−1 at 350 mV. The present study provides an advancement in the control of the electroless synthetic approach for the design and large-scale application of high-performance metal phosphide catalysts for electrochemical water splitting.

Surface decoration by means of metal nanostructures is an effective way to locally modify the electronic properties of materials. The decoration of ZnO nanorods by means of Au nanoparticles was experimentally investigated and modelled in terms of energy band bending. ZnO nanorods were synthesized by chemical bath deposition. Decoration with Au nanoparticles was achieved by immersion in a colloidal solution obtained through the modified Turkevich method. The surface of ZnO nanorods was quantitatively investigated by Scanning Electron Microscopy, Transmission Electron Microscopy and Rutherford Backscattering Spectrometry. The Photoluminescence and Cathodoluminescence of bare and decorated ZnO nanorods were investigated, as well as the band bending through Mott–Schottky electrochemical analyses. Decoration with Au nanoparticles induced a 10 times reduction in free electrons below the surface of ZnO, together with a decrease in UV luminescence and an increase in visible-UV intensity ratio. The effect of decoration was modelled with a nano-Schottky junction at ZnO surface below the Au nanoparticle with a Multiphysics approach. An extensive electric field with a specific halo effect formed beneath the metal–semiconductor interface. ZnO nanorod decoration with Au nanoparticles was shown to be a versatile method to tailor the electronic properties at the semiconductor surface.

A novel metal organic framework (MOF)-based composite was synthesized on a Cu substrate via a two-step route. An amorphous iron oxide/hydroxide layer was first deposited on a Cu foil through a sol–...

The decoration of semiconductor nanostructures with small metallic clusters usually leads to an improvement of their properties in sensing or catalysis. Bimetallic cluster decoration typically is claimed to be even more effective. Here, we report a detailed investigation of the effects of Au, Pt or AuPt nanocluster decoration of ZnO nanorods on charge transport, photoluminescence and UV sensitivity. ZnO nanorods were synthesized by chemical bath deposition while decoration with small nanoclusters (2-3 nm in size) was achieved by a laser-ablation based cluster beam deposition technology. The structural properties were investigated by scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry, and the optoelectronic properties by current-voltage and photoluminescence measurements. The extent of band bending at the cluster-ZnO interface was quantitatively modeled through numerical simulations. The decoration of ZnO nanorods with monometallic Au or Pt nanoclusters causes a significant depletion of free electrons below the surface, leading to a reduction of UV photoluminescence, an increase of ZnO nanorod dark resistance (up to 200 times) and, as a consequence, an improved sensitivity (up to 6 times) to UV light. These effects are strongly enhanced (up to 450 and 10 times, respectively) when ZnO nanorods are decorated with bimetallic AuPt nanoclusters that substantially augment the depletion of free carriers likely due to a more efficient absorption of the gas molecules on the surface of the bimetallic AuPt nanoclusters than on that of their monometallic counterparts. The depletion of free carriers in cluster decorated ZnO nanorods is quantitatively investigated and modelled, allowing the application of these composite materials in UV sensing and light induced catalysis. ispartof: NANOSCALE vol:12 issue:37 pages:19213-19222 ispartof: location:England status: published

There is a huge demand for rapid, reliable and low-cost methods for the analysis of heavy metals in drinking water, particularly in the range of sub-part per billion (ppb). In the present work, we describe the preparation, characterization and analytical performance of the disposable sensor to be employed in Square Wave Anodic Stripping Voltammetry (SWASV) for ultra-trace simultaneous determination of cadmium and lead. The electrode consists of graphene paper-perfluorosulfonic ionomer-bismuth nano-composite material. The electrode preparation implies a key step aimed to enhance the Bi3+ adsorption into nafion film, prior to the bismuth electro-deposition. Finely dispersed bismuth nanoparticles embedded in the ionomer film are obtained. The electrode was characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Electrochemical Impedance Spectroscopy (EIS). The electrode shows a linear response in the 5&ndash, 100 ppb range, a time-stability tested up to almost three months, and detection limits up to 0.1 ppb for both Pb2+ and Cd2+. The electrode preparation method is simple and low in cost and the obtained analytical performance is very competitive with the state of art for the SWASV determination of Pb2+ and Cd2+ in solution.

Zinc oxide (ZnO) nanostructures were synthesized in the form of nanoparticles, nanoflowers and nanourchins. Structural, electronic and optical characterization of the samples was performed via standard techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence, Raman and ultraviolet-visible (UV-Vis) spectroscopy. Point defect structures which are specific to each morphology have been investigated in terms of their concentration and location via state-of-the-art electron paramagnetic resonance (EPR) spectroscopy. According to the core-shell model, all the samples revealed core defects; however, the defects on the surface are smeared out. Finally, all three morphologies have been tested as electrode materials in a real supercapacitor device and the performance of the device, in particular, the specific capacitance and the storage mechanism, has been mediated by the point defects. Morphology-dependent defective ZnO electrodes enable the monitoring of the working principle of the supercapacitor device ranging from electric double-layer capacitors (EDLC) to pseudo-supercapacitors. © 2020 The Royal Society of Chemistry.

Earth-abundant materials for electrochemical water splitting typically show a lower efficiency than noble and rare metal electrocatalysts. Nanostructuring and appropriate material design can largely improve the performances of low-cost electrocatalysts, opening the route towards profitable mass production. Here, we report on a quantitative investigation of the oxygen evolution reaction (OER) on Ni-based nanowall (NW) electrodes. The NiO and Ni(OH)2 NW films (200 or 400 nm thick) are produced by chemical bath deposition followed by calcination at 350 °C. The morphology and the chemical arrangement of the NW were studied, before and after the OER, by scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The OER electrocatalytic activity was investigated by electrochemical measurements under alkaline conditions (1 M KOH), demonstrating a stable overpotential of 345 mV at 10 mA cm−2, a Tafel slope of 48 mV dec−1 and an O2 turnover conversion frequency (TOF) of up to 0.18 s−1. The quantitative measurement of active electrocatalysts, through cross-correlation of the experimental data, shows nearly 100% material utilization in the 200 nm NiO NW. In thicker NiO or Ni(OH)2 NW films this fraction decreases below 60%, probably due to the decrease in the electric potential along the nanostructure, as revealed by numerical simulation. These data and discussion support the use of low-cost Ni-based nanostructures for high-efficiency and sustainable electrocatalysts.

Nanostructured WO3 represents a promising material for electrochromic and sensing devices. In this scenario, electrodeposition is a promising low-cost approach for careful production. The electrodeposition of tungsten oxide film from a peroxo-tungstic-acid (PTA) solution is investigated. WO3 is synthetized onto Indium doped Tin Oxide (ITO) substrates, in a variety of shapes, from a fragmentary, thin layer up to a thick continuous film. Samples were investigated by scanning electron (SEM) and atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), X-ray Diffraction analysis (XRD), energy gap measurement. Electrodeposition current curves are compared with characterization results to model the growth process. Early stages of electrodeposition are characterized by a transient cathodic current revealing an instantaneous nucleation followed by a diffusion limited process. A quantitative analysis of W deposition rate and current at working electrode validates a microscopic model for WO3 electrodeposition driving the process towards nanostructured versus continuous WO3 film.

Zinc Oxide (ZnO) nanowalls (NWLs) are interesting nanostructures for sensing application. In order to push towards the realization of room-temperature operating sensors, a detailed investigation of the synthesis effect on the electrical and optical properties is needed. This work focuses on the low-cost synthesis of ZnO NWLs by means of chemical bath deposition (growth time of 5, 60, and 120 minutes) followed by annealing in inert ambient (temperature of 100, 200, and 300 &deg, C). The as-grown NWLs show a typical intertwined network of vertical sheets whose features (thickness and height) stabilize after 60 minutes growth. During thermal annealing, NWLs are converted into ZnO. The electric transport across the ZnO NWL network radically changes after annealing. A higher resistivity was observed for longer deposition times and for higher annealing temperatures, at which the photoluminescence spectra resemble those obtained for ZnO material. A longer deposition time allows for a better transformation to ZnO during the annealing, thanks to the presence of ZnO seeds just after the growth. These findings can have a significant role in promoting the realization of room-temperature operating sensors based on ZnO NWLs.

Energy storage performances of Ni-based electrodes rely mainly on the peculiar nanomaterial design. In this work, a novel and low-cost approach to fabricate a promising core-shell battery-like electrode is presented. Ni(OH)2@Ni core-shell nanochains were obtained by an electrochemical oxidation of a 3D nanoporous Ni film grown by chemical bath deposition and thermal annealing. This innovative nanostructure demonstrated remarkable charge storage ability in terms of capacity (237 mAh g−1 at 1 A g−1) and rate capability (76% at 16 A g−1, 32% at 64 A g−1). The relationships between electrochemical properties and core-shell architecture were investigated and modelled. The high-conductivity Ni core provides low electrode resistance and excellent electron transport from Ni(OH)2 shell to the current collector, resulting in improved capacity and rate capability. The reported preparation method and unique electrochemical behaviour of Ni(OH)2@Ni core-shell nanochains show potential in many field, including hybrid supercapacitors, batteries, electrochemical (bio)sensing, gas sensing and photocatalysis.

Energy storage performances of Ni-based electrodes rely mainly on the peculiar nanomaterial design. In this work, a novel and low-cost approach to fabricate a promising core-shell battery-like electrode is presented. Ni(OH)2@Ni core-shell nanochains were obtained by an electrochemical oxidation of a 3D nanoporous Ni film grown by chemical bath deposition and thermal annealing. This innovative nanostructure demonstrated remarkable charge storage ability in terms of capacity (237 mAh g−1 at 1 A g−1) and rate capability (76% at 16 A g−1, 32% at 64 A g−1). The relationships between electrochemical properties and core-shell architecture were investigated and modelled. The high-conductivity Ni core provides low electrode resistance and excellent electron transport from Ni(OH)2 shell to the current collector, resulting in improved capacity and rate capability. The reported preparation method and unique electrochemical behaviour of Ni(OH)2@Ni core-shell nanochains show potential in many field, including hybrid supercapacitors, batteries, electrochemical (bio)sensing, gas sensing and photocatalysis.

The massive production of nanostructures with controlled features and high surface area is a challenging and timely task in view of developing effective materials for sensing and catalysis. Herein, functional ZnO nanostructures, named microflowers (MFs) have been prepared by a facile and rapid chemical bath deposition. ZnO MFs show an intriguing sheets-composed spheroidal shape, with diameters in the range 0.2&ndash, 2.5 &micro, m, whose formation is achieved by a complexing action by F in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine. The evolution of the physical and structural properties of the material, following post-deposition thermal annealing, has been investigated by scanning electron microscopy (SEM), energy dispersive X-ray analyses (EDX), photoluminescence (PL) and X-ray diffraction (XRD) techniques. The effectiveness of ZnO MFs in UV detection has also been tested to account for the potentiality of these nanostructures.

A novel electrochemical device based on Nickel oxide sensing species is described. The miniaturized device contains three integrated metal microelectrodes with the working active electrode made of Ni zero-valence. It has been proved to be sensitive and versatile in the detection of glucose on saliva. The findings here reported pay the way to future development of versatile portable sensors addressing easy-to-use and low-cost system.

Hierarchical nanostructures composed of Ni(OH)2 nanoflakes on ZnO nanorods (NRs) are fabricated by a low-cost, fully chemical method at room-temperature. The morphological features of the ZnO NRs were varied (by changing the chemical bath deposition parameters) in terms of height and lateral size. ZnO NRs provide a large surface area substrate for the pulsed electrodeposition of nanostructured Ni(OH)2. The correlation between the synthetic parameters, the final structure and the electrochemical behavior of Ni(OH)2/ZnO nanostructures is investigated. The enzyme-free oxidation of glucose at the surface of electrodeposited Ni(OH)2 is demonstrated in 0.1 M NaOH, revealing that a proper choice of the electrodes fabrication conditions improves the glucose sensitivity up to 1.85 mA cm−2 mM−1, with a linear detection range of 0.04–2.10 mM. All the samples show a fast response time (less than 1 s), resistance in chloride solution, selectivity in the presence of common interfering electroactive species and excellent long-term stability. All these features, combined with the ease of the fabrication method, make Ni(OH)2/ZnO nanostructures an ideal alternative for inexpensive amperometric glucose sensing applications.

NiO nanowalls were grown by low-cost chemical bath deposition (CBD) method and thermal annealing. SEM analysis showed a high surface area and porous thin film formed by a network of ~20 nm thick and ~270 nm tall nanosheets. NiO nanowalls were prepared onto interdigitated electrodes and applied for acetone sensing. The response transients at various temperatures were recorded an successfully modelled by two adsorption sites. Both sites are active below 250 °C, while only the site with shorter response time is active above 250 °C. At the optimal temperature of 250 °C, the sensor demonstrated high sensitivity to acetone (1–40 ppm), a low limit of detection (LoD) of ~200 ppb and good selectivity. These unique features combined with the low-cost and simple fabrication process make it a cheap and efficient acetone sensor.

NiO-based NO2 sensors operating at room temperature are attracting great attentions due to their promising energy and cost saving performances. However, only a few reports showed high sensitivity and selectivity in the sub-ppm concentration range and low limit of detection (LoD). In this work, we designed and fabricated by a low-cost chemical bath deposition (CBD) and thermal annealing a nanostructured and porous NiO thin film (nanoporous NiO film) composed of NiO nanoparticles (30−50 nm). The nanoporous NiO film was then applied as sensing element for the NO2 detection at room temperature, demonstrating a high response to sub-ppm level NO2 (140 ppb), excellent selectivity and stability, and a very low LoD of 20 ppb. The NO2 sensing mechanism was investigated and satisfactorily modelled by two energetically different and independent adsorption sites at room temperature. Both sites contribute to the NO2 detection at room temperature while only one site contributes at higher temperatures. The described low-cost fabrication method and the discussed superior NO2 sensing performances at room temperature make the nanoporous NiO film a promising NO2 sensor for environmental monitoring.

Correction for ‘High intrinsic activity of the oxygen evolution reaction in low-cost NiO nanowall electrocatalysts’ by Salvatore Cosentino et al., Mater. Adv., 2020, DOI: 10.1039/d0ma00467g.

This work focuses on the synthesis and gas sensing properties of ZnO nanowalls (ZnO NWLs) grown by a simple cheap chemical bath deposition method on a thin layer of aluminum (about 20 nm thick) printed on the Pt interdigitated electrodes area of conductometric alumina platforms. Post-deposition annealing in nitrogen atmosphere at 300 °C enabled the formation of a ZnO intertwined 2D foils network. A wide characterization was carried out to investigate the composition, morphology and microstructure of the nanowalls layer formed. The gas sensing properties of the films were studied by measuring the changes of electrical resistance upon exposure to low concentrations of carbon monoxide (CO) and nitrogen dioxide (NO2) in air. The sensor response to CO or NO2 was found to be strongly dependent on the operating temperature, providing a means to tailor the sensitivity and selectivity toward these selected target gases.

In this work, two natural dyes extracted from henna and mallow plants with a maximum absorbance at 665 nm were studied and used as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). Fourier transform infrared (FTIR) spectra of the extract revealed the presence of anchoring groups and coloring constituents. Two different structures were prepared by chemical bath deposition (CBD) using zinc oxide (ZnO) layers to obtain ZnO nanowall (NW) or nanorod (NR) layers employed as a thin film at the photoanode side of the DSSC. The ZnO layers were annealed at different temperatures under various gas sources. Indeed, the forming gas (FG) (N2/H2 95:5) was found to enhance the conductivity by a factor of 103 compared to nitrogen (N2) or oxygen (O2) annealing gas. The NR width varied between 40 and 100 nm and the length from 500 to 1000 nm, depending on the growth time. The obtained NWs had a length of 850 nm. The properties of the developed ZnO NW and NR layers with different thicknesses and their effect on the photovoltaic parameters were studied. An internal coverage of the ZnO NWs was also applied by the deposition of a thin TiO2 layer by reactive sputtering to improve the cell performance. The application of this layer increased the overall short circuit current Jsc by seven times from 2.45 × 10−3 mA/cm2 to 1.70 × 10−2 mA /cm2.

An effective electrode modification strategy, integrated in a miniaturized silicon biosensor, was investigated for the rapid and sensitive electrochemical detection of low amount of DNA without PCR step. The miniaturized biosensor here presented is composed of three planar microelectrodes for electrochemical transduction of hybridized DNA target on working electrode, the hybridization is probed by the intercalation of Osmium redox probe.

Photon absorption in the solar energy range has been investigated in semiconductor nanostructures. Different synthesis techniques (magnetron sputtering, plasma enhanced chemical vapor deposition, ion implantation) followed by thermal annealing, have been employed to fabricate Si or Ge nanoclusters (1-25 nm in size) embedded in SiO2or Si3N4matrices. The thermal evolution in the formation of Si nanoclusters (NCs) in SiO2was shown to depend on the synthesis technique and to significantly affect the light absorption. Experimentally measured values of optical bandgap (EgOPT) in Si NCs evidence the quantum confinement effect which significantly increases the value ofEgOPTin comparison to bulk Si.EgOPTspans over a large range (1.6-2.6 eV) depending on the Si content, on the deposition technique and, in a most significant way, on the structural phase of NC. Amorphous Si NCs have a lowerEgOPTin comparison to crystalline ones. The matrix effect on the synthesis and light absorption in semiconductor NCs was investigated for Ge NCs. Large difference in the Ge NCs synthesis occurred when using SiO2or Si3N4matrices, essentially due to a much lower Ge diffusivity in the latter, which slows down the formation and growth of Ge NCs in comparison to silica matrix. Light absorption in NCs is also shown to be largely affected by the host matrix. Actually, Ge NCs embedded in Si3N4material absorb photons in the solar energy range with a higher efficiency than in silica, due to the different confinement effect. In fact, Si3N4host offers a lower potential barrier to photogenerated carriers in comparison to silica, thus a lower confinement effect is expected, leading to slightly smaller optical bandgap. These effects have been presented and discussed for potential application in light harvesting purposes.

International audience; The production of high-quality semiconducting nanostructures with optimized electrical, optical, and electromechanical properties is important for the advancement of next-generation technologies. In this context, we herein report on highly obliquely aligned single-crystalline zinc oxide nanosheets (ZnO NSs) grown via the vapor−liquid−solid approach using r-plane (01−12) sapphire as the template surface. The high structural and optical quality of as-grown ZnO NSs has been confirmed using high-resolution transmission electron microscopy and temperature-dependent photoluminescence, respectively. To assess the potential of our NSs as effective building materials in high-performance flexible electronics, we fabricate organic (parylene C)/inorganic (ZnO NS) hybrid field-effect transistor (FET) devices on flexible substrates using room-temperature assembly processes. Extraction of key FET performance parameters suggests that as-grown ZnO NSs can successfully function as excellent n-type semiconducting modules. Such devices are found to consistently show very high on-state currents (Ion) > 40 μA, high field-effect mobility (μeff) > 200 cm2/(V s), exceptionally high on/off current modulation ratio (Ion/off) of around 10^9, steep subthreshold swing (s-s) < 200 mV/decade, very low hysteresis, and negligible threshold voltage shifts with prolonged electrical stressing (up to 340 min). The present study delivers a concept of integrating high-quality ZnO NS as active semiconducting elements in flexible electronic circuits.

We study the optical properties of ZnO nanorods (NRs) fabricated by chemical bath deposition, hydrothermal, and the vapour-liquid-solid method (VLS). Scanning electron microscopy demonstrates differences in the structural properties for the various samples. The optical emission properties are studied by photoluminescence (PL) spectroscopy where all samples are characterized by a UV and visible emission band. The visible emission band is due to defects in the nanorods. VLS samples show a blue shift in the visible region of the PL spectra with respect to the other samples, however, all three samples are fitted with the same three visible Gaussian components under varying percent contributions due to the structural differences. The visible defect components are characterized by blue (B), green (G), and orange (O) states with energies at 2.52 eV, 2.23 eV, and 2.03 eV, respectively. The applicability of this universal model for visible B-G-O defects is tested against the literature and successfully fitted regardless of the fabrication method. Differences in the percentage contribution for the visible B-G-O defects is explained by variations in the fabrication method. This model indicates how defects can be controlled based on the fabrication method. Furthermore, the B state, which is associated with the 'green luminescence band', results from a transition from the defect level to the valence band, or possibly a shallow-acceptor, according to photoluminescence excitation measurements. The role of the B state in sensing applications is discussed.

Colloidal Ge nanocrystals (NCs) are gaining increased interest because of their potential application in low-cost optoelectronic and light harvesting devices. However, reliable control of colloidal NC synthesis is often an issue and a deeper understanding of the key-role parameters governing NC growth is highly required. Here we report an extended investigation on the growth of colloidal Ge NCs synthesized from a one-pot solution based approach. A systematic study of the effects of synthesis time, temperature and precursor concentration is elucidated in detail. X-ray diffraction (XRD) analysis reveals the presence of crystalline Ge NCs with a mean size (from 5 to 35 nm) decreasing with the increase of precursor concentration. Such a trend was further confirmed by scanning electron microscopy (SEM) and dynamic light scattering (DLS) analysis. Moreover, the temporal NC size evolution shows a typical saturating behaviour, where characteristic time shortens at higher precursor concentration. All these growth features were satisfactorily simulated by a numerical NC growth model, evidencing that the kinetics of NC growth is controlled by a reaction-limited regime with typical activation energy of 0.7 eV. Finally, light absorption in the visible region and the successful realization of a hybrid photodetector, employing colloidal Ge NCs embedded in PEDOT:PSS polymer, showed the capability of low-cost colloidal Ge to act as light harvester. These results put new understanding for a reliable control of colloidal NC growth and the development of low-cost devices.

In this work we propose an alternative methodology to study B diffusion in crystalline Ge. We enhance B diffusion by means of passing implants in such a way to increase the point-defects distribution through the sample, well above the equilibrium value. A comparison between B diffusion occurring under implantation with different ions or after post-implantation annealing allowed to discern any possible role of ionization effects on B diffusion. Indeed, B diffusion is demonstrated to occur through a point-defect-mediated mechanism. The diffusion mechanism is hence discussed. These results are a key point for a full comprehension of the B diffusion in Ge.

Transmission Electron Microscopy was combined with Time Resolved Reflectivity to study the amorphous-crystalline (a-c) interface evolution during Solid Phase Epitaxy Regrowth (SPER) Of Si0.83Ge0.17 films deposited on Si by Molecular Beam Epitaxy and amorphized with Ge+ ion implantation. Starting from the Si/SiGe interface, a 20 nm thick layer regrows free of defects with the same SPER rate of pure Si. The remaining SiGe regrows with planar defects and dislocations, accompanied by a decrease of the SPER velocity. The sample was also studied after implantation with B or P. In these cases, the SPER rate raises following the doping concentration profile, but no difference in the defect-free layer thickness was observed compared to the un-implanted sample. On the other hand, B or P introduction reduces the a-c interface roughness, while B-P co-implantation produces roughness comparable to the un-implanted sample. (c) 2007 Elsevier B.V. All rights reserved.

The role of the interface potential on the effective mass of charge carriers is elucidated in this work. We develop a new theoretical formalism using a spatially dependent effective mass that is related to the magnitude of the interface potential. Using this formalism, we studied Ge quantum dots (QDs) formed by plasma enhanced chemical vapour deposition (PECVD) and co-sputtering (sputter). These samples allowed us to isolate important consequences arising from differences in the interface potential. We found that for a higher interface potential, as in the case of PECVD QDs, there is a larger reduction in the effective mass, which increases the confinement energy with respect to the sputter sample. We further understood the action of O interface states by comparing our results with Ge QDs grown by molecular beam epitaxy. It is found that the O states can suppress the influence of the interface potential. From our theoretical formalism, we determine the length scale over which the interface potential influences the effective mass.