The atomic structures of nanoscale contacts are not available in most experiments on quantum transport. Scanning tunneling microscopy operates at a tip-sample distance of a few angstroms and relies on probing a conductive surface in the evanescent tail of electronic states. By decreasing the tip-sample distance the sensitivity to chemical interactions can be enhanced. This has already been demonstrated in non-contact atomic force microscopy, where the oscillating tip comes for short periods of time within the range of chemical interactions. A team of scientists has now developed Quantum Point Contact Microscopy as a novel imaging mode of low-temperature STM, where instead of measuring a current through a tunneling junction, a transport current through a quantum point contact formed by a single atom between the STM tip and the surface is recorded.
Nanoindentation is derived from the classical hardness test but is carried out on a much smaller scale. It can be used to determine the hardness of thin layers as well as material properties such as elasticity, stiffness, plasticity, and tensile strength, or fracture toughness of small objects and microsystems in fields such as biotechnology. These measurements involve applying a small force to a sample using a sharp probe and measuring the resultant penetration depth. The measured value is used to calculate the contact area and hence the particular property of the sample material. Both the method of force application and the geometry of the indentation tip can be adjusted to suit the particular application.
Life as we know it is dominated by friction, the interaction between moving objects. Friction controls our everyday lives, from letting us walk to work, to holding a cup of tea. Friction forces act wherever two solids touch. Although friction has been investigated for hundreds of years - in the 15th century, Leonardo da Vinci was the first to enunciate two laws of friction - it is surprisingly difficult to examine how friction works at the nanoscale level due to the sheer difficulty of bringing nanoscale objects into contact and imaging them at the same time. Researchers have now demonstrated the ability to bring nanoscale objects together, rub them repeatedly across one another and see how friction changes nanosized materials in real time.
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.