Discovering high performing organic semiconductors is a hot area of research, as we look for efficient, low-cost materials that can be used in inexpensive electronic devices, such as flexible solar cells and radio frequency ID tags. To design effective materials, the relationship between a material’s structure and its semiconductive properties must be found. Research on p-type (hole conducting) organic semiconductors has shown π-bond stacking to be important in determining the semiconducting properties. The newer, n-type (electron conducting) class of organic semiconductors has not been as extensively studied.
A desire to create machines that can explore their environments, like people do, through the sensations of feeling and touch, has inspired researchers to develop artificial skin. An ideal electronic skin would be flexible and sensitive to even minor touches, such as the weight of an insect. Such a touch-sensitive material could be used for human prosthetics, sensory input devices for robotics, and applications where the biologic and electronic communicate.
Currently, organic or plastic solar cells are relatively inexpensive to make, yet they are also relatively inefficient. Researchers from Princeton University and SSRL recently studied the structure of organic solar cells that were manufactured and processed in different ways to better understand the causes of the inefficiencies.
Organic or plastic solar cells have achieved efficiencies greater than 8%, close to the estimated 10% needed to make them economically viable. To close the gap, researchers need to improve control of the nanostructure of the active layer of these organic solar cells.
Organic semiconductors could usher in an era of foldable smart phones, better high-definition television screens and clothing made of materials that can harvest energy from the sun needed to charge your iPod or iPad, but there is one serious drawback: Organic semiconductors, while inexpensive, do not conduct electricity very well.
Materials that exhibit magnetism, superconductivity (the ability of electrons to travel without resistance across a material), and ferroelectricity (important for capacitors and used, for example, in medical ultrasound machines, infrared cameras and fire sensors) are the subject of significant scientific and technological research. These properties can depend strongly on the roughness of interfaces between layers as well as the thickness of these layers (often each a mere ~2.5 nanometers, or 1/16,000th the width of a human hair, thick); as such, the ability to characterize these layers at high-resolution is important. Yet few characterization techniques exist that have the ability to characterize the structure and uniformity of such complex structures.
Increasing the speed and complexity of semiconductor integrated circuits requires advanced processes that put extreme constraints on the level of metal contamination allowed on the surfaces of silicon wafers. Such contamination degrades for example the performance of the ultra thin SiO2 gate dielectrics (< 4nm) that form the heart of the individual transistors. Ultimately, reliability and yield are reduced to levels that must be improved before new processes can be put into production. Much of this metal contamination occurs during the wet chemical etching and rinsing steps required for the manufacture of integrated circuits and industry is actively developing new processes that have already brought the metal contamination to levels beyond the detection capabilities of conventional analytical techniques.
Attempting to determine and describe the atomic arrangements in an amorphous material is a daunting prospect. A considerable advance has been made in the anomalous X-ray scattering approach to determining these arrangements in materials containing two atomic species.
Many condensed matter systems can be described as large collections of microscopic entities, each of which can be in one of two possible states. For example, in many anisotropic magnets spins can point in one of two directions along a unique crystalline axis. In a liquid-gas phase transition, molecules will be in either the gas or liquid phase. When the microscopic entities interact, they may exhibit collective long-range order. A collection of two-state particles with near-neigh bor interactions is known as an Ising system. This simple system is very important because the behavior that an Ising system displays as it undergoes a transition to long-range order has universal features that are independent of the details of the two-state particles or their interaction.
The famous 17th-century Swedish warship Vasa has been on display in the Vasa Museum since 1990 (Figure 1). The Vasa sank on its maiden voyage in 1628, and was recovered in 1961 after 333 years in the cold brackish water of Stockholm harbor. After extensive conservation treatment, the oaken Vasa appeared in good condition (1). However, high acidity and a rapid spread of sulfate salts and elemental sulfur were recently observed on many wooden surfaces. A research team led by Prof. Magnus Sandström, University of Stockholm, have approached the problem by using X-ray absorption near edge spectroscopy (XANES) at the sulfur K-edge.
