Metrology is the science of measurements, and nanometrology is that part of metrology that relates to measurements at the nanoscale. Many governments worldwide have existing nanotechnology policies and are taking the preliminary steps towards nanometrology strategies, for example in support of pre-normative R+D and standardization work. In this Nanowerk Spotlight, we look at the European Commission funded project Co-Nanomet as an example of the importance of nanometrology as a key enabling technology for quality control at the nanoscale. While a first and obvious benefit of metrology is its potential to improve scientific understanding, a second, equally important, but less obvious benefit of metrology is closely linked to the concepts of quality control or conformity assessment, which means making a decision about whether a product or service conforms to specifications.
The copper Damascene electrodeposition is a key fabrication process, currently used in state-of-the-art, multilevel copper metallization of microelectronic interconnects that range from transistor to circuit board length scale. This strongly technology-driven application serves as a key motivator for applied and fundamental mechanistic studies that can spur further development and optimization of the copper electrodeposition process. This report effectively demonstrates the ability of the FlexAFM to monitor morphological changes during electrodeposition of material on an electrode surface. In the data shown here, copper was deposited on a flame annealed gold surface. The deposition process was shown to be fully reversible: At low potentials copper was deposited and at higher potentials it was dissolved again. Deposition and dissolution took place very rapidly, within one AFM scan line.
Graphene is a very interesting nanomaterial with potential for applications in many different fields including nanoelectronics. However, the properties of graphene can vary broadly and depend sensitively on its integration in device structures and the details of its interaction with other materials, such as underlying substrates or gate dielectrics. Unlike other semiconductor electronic devices, where the active layer is buried below the surface and where microscopic details of transport cannot be directly examined, graphene is exposed at a surface and can be directly examined on the atomic scale using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). New work now provides microscopic details of graphene interaction with a substrate in the most common device structure used so far.
Ranging from electronic gadgets to medical applications, many nanomaterial-based devices have appeared in the market. One of the most important issues for these devices is their reliability and life-time of operation. A vital factor behind these issues is the structural stability of the nano-device - debonding of the nanomaterial from the substrate material being the single largest contribution for device degradation. In order to improve bonding between nanomaterials and their substrate, it is essential to understand and quantify the bonding mechanisms. A new nano-scratch technique developed by researchers in the U.S. could serve as the basis for a reliable quantification technique for interpreting nanomaterial-substrate bond strength.
In atomic force microscopy (AFM), tip quality depends mainly on the dimensions and shape of the probe, the durability of the tip apex, and the nature of the interaction between sample and probe. With this in mind, researchers have experimented with mounting ultra sharp and high aspect ratio carbon nanotube (CNT) bundles onto the apex of an AFM tip to improve spatial and potential resolution. Although AFM tips functionalized with a carbon nanotube have attracted considerable attention, attaching CNTs to scanning probes is not a trivial matter, which limits their practical use. An alternative approach, whereby a CNT is grown onto the AFM tip, also can be very time-consuming and requires a costly set-up. A team at the Friedrich-Schiller-University Jena in Germany has now demonstrated a fast and cheap process for the fabrication of carbon nanotube AFM tips with the help of microwave ovens.
Plastic solar cells are emerging as alternative energy sources for the future because of their potential for cheap roll-to-roll printing, ease of processing, light-weight and flexibility. However, their current performance is still low for practical applications which partially originate from the poor understanding of device physics and nanoscale morphology of the photoactive layer. Photoconductive atomic force microscopy (pcAFM)is a powerful characterization tool to better understand the complex optoelectronic and morphological phenomena of organic solar cells at the nanoscale. This article briefly described the applicability of the pcAFM technique for analyzing solution-processed, polymer and small molecule bulk heterojunction solar cells. Due to the nature of charge generation, transport and collection occurring at the nanometer scale, the useful information on device operation can be lost from macroscopic measurements.
An intriguing novel approach to extract the energy from the photosynthetic conversion process has been demonstrated by researchers at Stanford and Yonsei Universities. They have inserted ultrasharp gold nanoelectrodes into living algae cells and extracted electrons, thereby harnessing an - albeit very tiny - electrical current. This is electricity production that doesn't release carbon into the atmosphere. The results demonstrate the feasibility of collecting high-energy electrons in steps of the photosynthetic electron transport chain and prior to the downstream processes associated with energy loss. In addition, the system allows direct monitoring of specific charge transfer reactions in live cells, leading to broad applications for investigating developmental processes and the responses of cells and organelles to light and chemical stimuli.
Most of the material properties investigated by atomic force microscopy are acquired by processing the deflection signal of the cantilever, which is applied to Electrostatic Force Microscopy (EFM) measurements as well. For EFM, the sample surface properties would be electrical properties and the interaction force will be the electrostatic force between the biased tip and the sample. Electrostatic Force Microscopy maps electric properties on a sample surface by measuring the electrostatic force between the surface and a biased AFM cantilever. EFM applies a voltage between the tip and the sample while the cantilever hovers above the surface, not touching it. The cantilever deflects when it scans over static charges.