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We present a study of the effect of gold nanoparticles (Au NPs) on TiO2 on charge generation and trapping during illumination with photons of energy larger than the substrate band gap. We used a novel characterization technique, photoassisted Kelvin probe force microscopy, to study the process at the single Au NP level. We found that the photoinduced electron transfer from TiO2 to the Au NP increases logarithmically with light intensity due to the combined contribution of electron-hole pair generation in the space charge region in the TiO2-air interface and in the metal-semiconductor junction. Our measurements on single particles provide direct evidence for electron trapping that hinders electron-hole recombination, a key factor in the enhancement of photo(electro)catalytic activity., This work was supported by the Office of Basic Energy Sciences (BES) of the U.S. Department of Energy (DOE) under contract DE-AC02-05CH11231 through the Structure and Dynamics of Materials Interfaces Program (FWP KC31SM) and the Molecular Foundry. M.L. acknowledges funds from Comunidad de Madrid (P2018/EMT-4308), a Fulbright grant PRX16/00564, and the MCIU-AEI-FEDERUE (RTI2018-096937-B-C22 and MAT2014-59772-C2-1-P). J.C. acknowledges financial support from Ministerio de Ciencia e Innovación (MICINN) and the European Union through the project PID2019-104272RB-C52. Also, Y.H. acknowledges financial support from MCIU through MAT2014-59772-C2-2- P and L.M. from EC through ERC-2013-SYG-610256. V.A.P.O. and M.B. acknowledge the financial support from EC through ERC CoG HyMAP 648319, MINECO PID2019- 106315RB-I00 and ENE2017-89170-R, ″Comunidad de Madrid″ and European Structural Funds (FotoArt-CM project S2018/NMT-4367) and Fundación Ramón Areces (Art-Leaf project). M.B. also thanks the Juan de la Cierva Incorporación contract (IJC2019042430-I). X.Z. was supported by the NSF-BSF 359 grant number 1906014. The authors thank Prof. Eran Edri, María Ujué González Sagardoy, and Judit Meseguer- Oliver for fruitful discussions and Asylum customer support for help with modifications of the AFM.

For more than 50 years, Moore's law has creatively captured how the capability of electronics has expanded by creating ever smaller devices and exploiting new materials and devices. Critical to maintaining that trajectory of increased capability of electronics has been the creation of new and ever-more sensitive measurement techniques to guide invention and fabrication. Quantum effects, which are already important in roomtemperature semiconductor devices small in size, are key to the creation of this future technology. Further, many quantum effects arise at very low temperatures or with 1D and 2D materials and devices. This is motivating new metrology techniques at very low temperature, which assist in exploring these new phenomena for understanding and commercialization.

This paper discusses advancements that have been made in scanning microwave impedance microscopy (sMIM) and how they are being used to measure various electrical properties in semiconductor devices. It explains that sMIM has a sensitivity of less than 0.1 aF and can measure minute changes in dielectric constant (k-value) and distinguish dopant levels over a wide range of concentrations with a spatial resolution of a few nm. For dielectric films and dopant levels, measurements are conveniently given in log-linear form with a repeatability well within the typical requirements for process monitoring. This, in turn, has enabled reliable quantification, where once only qualitative information was provided. The paper presents real-device results representing a wide range of measurement scenarios.

Metrology of the properties of materials is a growing concern in semiconductor manufacturing and as a result, new and existing technologies are being adapted to address gaps in established capabilities. We introduce here Scanning Microwave Impedance Microscopy (sMIM), a technology that can measure critical material properties such as dielectric constant (k-value), capacitance, resistivity and permittivity at the nanoscale. In this technique, an AFM cantilever is used as a microwave source to measure the electrical properties of materials at nanometer scale. sMIM is sensitive to the local capacitive and conductivity changes in a material making it an excellent method to apply on a wide range of materials such as insulators, semiconductors, ferroelectrics and other. An sMIM measurement provides the permittivity and conductivity of films. From this measurement you can derive properties such as dopant concentration, resistivity and identify certain defects. Since microwaves can penetrate deep into the sample, we can measure sub-surface layers as well. The resolution of the sMIM ScanWave system for capacitance measurements has been calculated to be better than 0.3 aF and the repeatability is well below 1% RSD 1σ making suitable for very sensitive process control of dielectric films and dopant concentration. Types of measurements presented here include nano C-V for dielectric film quality, dielectric film k value and dopant concentration. Additional applications are envisioned in emerging memory materials.

The use of sacrificial self-assembled monolayers (SAMs) to prepare clean n-type GaAs (100) surfaces without band bending in vacuo is demonstrated. GaAs surface passivation using octadecanethiol SAMs after HCl cleaning is shown to lead to an enhancement of the room-temperature photoluminescence intensity. Synchrotron-radiation photoelectron spectroscopy (SRPES) finds that the interfacial oxide between GaAs and the SAM remains below the detection limit. Evidence for both Ga–S and As–S bonds at the GaAs–thiolate interface is found. The limited thermal stability of the SAM allows the desorption of the alkyl chains by in situ thermal annealing at temperatures above 180 °C, leaving S bonded to Ga behind. The resulting surface contains only a very small amount of O (0.05 ML coverage) and C (about 3% of the SAM remaining) and shows no band bending with the surface Fermi level close to the conduction band. Atomic layer deposition of Al2O3 on this surface occurs via the formation of Al–S bonds without introducing a...

Solution processed polymer (donor) and fullerene (acceptor) bulk heterojunctions are widely used as the photo active layer in organic solar cells. Intimate mixing of these two materials is essential for efficient charge separation and transport. Identifying relative positions of acceptor and donor rich regions in the bulk heterojunction with nanometer scale precision is crucial in understanding intricate details of operation. In this work, a combination of Ar(+)2000 gas cluster ion beam and scanning probe microscopy is used to examine the lateral and vertical phase separation within regio-regular poly(3-hexylthiophene)(P3HT):phenyl-C60-butyric acid methyl ester (PCBM) bulk heterojunction. While the Ar(+)2000 gas cluster ion beam is used as a sputter tool to expose the underneath layers, scanning probe microscopy techniques are used to obtain two-dimensional (2D) electrical maps (with sub-2 nm lateral resolution). The electrical mapping is decoded to chemical composition, essentially producing lateral and vertical maps of phase separation. Thermal stress causes large PCBM-rich hillocks to form, and consequently affecting the balance of P3HT:PCBM heterojunctions, hence a negative impact on the efficiency of the solar cell. We further developed a method to analyze the efficiency of exciton dissociation based on the current maps and a loss of 20% in efficiency is observed for thermally degraded samples compared to fresh un-annealed samples.

We examine degradation of Ta2O5 high-k oxide.Effect of recrystallization on the electrical properties of Ta2O5 is investigated.Poly-crystalline Ta2O5 shows different conductive domains.Conductive atomic force microscopy (C-AFM) and TEM are used for characterization. In this work, we observe the morphological and electrical changes induced in poly-crystalline Ta2O5 upon thermal treatment. The correlation between the morphological structure and the conductivity patterns is done by conductive atomic force microscopy (C-AFM) in plain view and cross sectional with transmission electron microscopy (TEM). Morphologically we observe grain boundaries developing into small gaps creating a network of insulating material running across the entire surface. We also observe decoration of the grain boundaries with some highly conductive particles which based on the TEM observations correspond to TaN clusters which apparently are formed during the crystallization. Increased leakage is observed by C-AFM at the edges of the crystalline grains consistent with the TEM observation of a reduction in thickness and a less ordered crystalline lattice for the Ta2O5. These results clearly demonstrate the impact of thermal treatment on the film properties, the defects formation and dielectric degradation in high-k materials.

Self assembled monolayers derived from amino silane precursors (C 11 NH 2 ) are studied using conductive AFM (C-AFM) technique in high vacuum (HV) conditions (∼5 × 10 −5 torr). Working in HV condition was preferred to working in air in order to reduce the impact of water meniscus on the surface which increases the adhesion forces causing smearing of the SAMs. C-AFM current maps of these samples indicate a decrease in the number of leakage spots with an increase in the deposition time. The latter is indicative of a trend towards a complete coverage of SAMs for the higher deposition times. To further assess the electrical properties of the SAMs, point I – V spectroscopy measurements were performed up to the point of electrical breakdown. The breakdown voltage increases with the increase in the number of multilayers for the 3 h, 6 h, and 18 h deposition time and then drops for the 24 h deposition time. In this final case we speculate that the numbers of impurity sites are higher and the charge carriers need less electric field to tunnel to the nearest site.

A simple fabrication scheme for molecular electronic junctions is presented with multiwalled carbon nanotubes (MWCNTs) as the top electrodes. Results indicate that our approach retains the molecular character of the chosen molecules [a self-assembled monolayer of octadecanethiol on gold bottom electrodes] and opens the door for studying a wide variety of organothiol candidates for molecular electronics. The fabrication scheme is designed in a way that it can be modified into all-carbon devices in the future by using graphitic carbon bottom electrodes functionalized with nitrozoabenzene, for example, and MWCNTs or graphene as the top electrodes. Alternatively, the scheme is applicable for all-gold devices with gold bottom electrodes and gold nanowire top electrodes.

© 2015 AIP Publishing LLC. Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III-V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III-V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of different chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally

The tunneling current through an atomic force microscopy (AFM) tip is used to evaluate the effective electrical contact area, which exists between tip and sample in contact-AFM electrical measurements. A simple procedure for the evaluation of the effective electrical contact area is described using conductive atomic force microscopy (C-AFM) in combination with a thin dielectric. We characterize the electrical contact area for coated metal and doped-diamond tips operated at low force (