Microstructure of low temperature grown AlN thin films on Si(111)

AlN thin films were grown on HF-etched Si(111) substrates at 400–600 °C400–600°C by plasma source molecular beam epitaxy. Reflection high energy electron diffraction and transmission electron microscopy studies show that AlN films grown at 400 °C400°C form an initial amorphous region at the interface, followed by cc-axis oriented columnar grains with slightly different tilts and twists. AlN films grown at 600 °C600°C showed a significantly reduced amorphous region near the interface promoting an epitaxial growth of AlN with AlN[0001]∥Si[111]AlN[0001]∥Si[111] and AlN[010]∥Si[11]AlN[011̄0]∥Si[112̄] orientations. However, all the films show numerous defects such as stacking faults, dislocations, and grain boundaries. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71269/2/JAPIAU-85-11-7879-1.pd

Interface structure and surface morphology of (Co, Fe, Ni)/Cu/Si(100) thin films

We have examined bilayer Co/Cu, Fe/Cu, and Ni/Cu films deposited by molecular‐beam epitaxy on hydrogen‐terminated [100] silicon substrates. The magnetic metal/copper interface was examined by atomic resolution transmission electron microscopy and compared with the surface morphology as depicted by atomic force microscopy. The general orientation relationships across the magnetic metal/copper interfaces were found to be: [001]Co, Ni∥[001]Cu; (010)Co, Ni∥(010)Cu and [001]Fe∥[001]Cu; (110)Fe∥(200)Cu. The latter system is equivalent to the [11 1]Fe∥[011]Cu and (110)Fe∥(100)Cu Pitsch relationship, as has been reported earlier. Furthermore, there was a general correlation between interfacial and surface roughness, indicating that the initial interface character is propagated throughout the film during growth. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71022/2/JAPIAU-80-9-5035-1.pd

Disorder effects on infrared reflection spectra of InN films

The effect of plasmon and LO-phonon damping on the optical measurements of InN films is discussed. Phonon and plasmon damping dramatically modifies the spectral features of the optical spectra and destabilizes the coupled modes of the system. Phonon damping affects the optical properties in a qualitatively different way from plasmon damping. Increased phonon damping leads to a merging of the coupled modes for a certain range of carrier density. Plasmon damping broadens the spectral linewidths of both of the coupled modes when plasmon energies are of the order of LO-phonon energies. However, when plasmon energies are larger than LO-phonon energies, increasing plasmon damping makes the higher-energy mode completely degenerate with plasmon, and may even have lower energies than plasmon. In weakly damped situations, we also discuss the low-energy optical transmission region that forms in between the coupled modes. Finally, the effect of plasmon and LO-phonon coupling on the analyses of the experimental infrared reflection data of InN films (for different electron densities) is discussed. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71000/2/JAPIAU-95-9-4795-1.pd

Effect of [111] texture on the perpendicular magnetic anisotropy of Co/Ni multilayers

[111]fcc[111]fcc oriented [Co(2 Å)/Ni(7 Å)]20[Co(2Å)/Ni(7Å)]20 multilayers were prepared by molecular beam epitaxy at room temperature on epitaxial Au/Ag buffer layers grown on chemically etched Si(111) surfaces. NH4FNH4F etching of Si(111) leads to a smaller spread in the 〈111〉 orientation of the Au/Ag buffer layers and the Co/Ni multilayers as compared to a similar sample prepared on HF-etched Si(111). This results in a stronger perpendicular magnetic anisotropy as determined from the magnetic hysteresis loops. Cross-sectional transmission electron microscopy studies show that the magnetic multilayer film is not flat but has significant waviness at both top and bottom surfaces. The observed waviness originates in part from the waviness already present on the surface of the Au buffer layer and appears to be further enhanced by the difference in the surface free energies of Au and the magnetic elements. A flatter Au/Ag buffer layer is essential to further improve the [111] texture of the [Co/Ni] multilayers. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69592/2/JAPIAU-84-6-3273-1.pd

Pd/Cr Gates for a MIS Type Hydrogen Sensor

Instead of the pure Pd gates in MIS type hydrogen sensor, Pd-Cr alloy gates with different composition and structure were used to improve the sensors performance. The use of Pd-Cr alloy not only extended the dynamic range from 100 ppm to 50,000 ppm of hydrogen, but also showed quick response. The dynamic range and sensitivity were related to the nature of metal outer surface and the metal/insulator interface respectively

Performance of a MIS Type Pd-Cr/AlN/Si Hydrogen Sensor

An MIS Hydrogen sensor with a Pd0.96Cr0.04/AlN/Si structure was fabricated, exhibiting the dynamic range considerably wider than that of analogous devices with pure Pd gates. A useful response could be obtained for Hydrogen concentrations as large as 50,000 ppm. Although the response amplitude was much reduced at the lower concentrations, satisfactory signal to noise down to 50 ppm could be obtained. The saturating magnitude of the electrical response is in the range of 0.1 to 0.5 V, which is the same as that for the pure Pd gated devices, inspite of the 3 orders of magnitude difference in the saturation hydrogen concentration. This result will be discussed in terms of the response mechanism of these devices

Raman spectral signatures of mouse mammary tissue and associated lymph nodes: normal, tumor and mastitis

Raman spectroscopy involves the interaction of light with the molecular vibrations and therefore can provide information about molecular structure, tissue composition and changes in its environment. We explored whether Raman spectroscopy can reliably distinguish mammary tumors from normal mammary tissues and other pathological states in mice. We analyzed a large number of Raman spectra from the tumor and normal mammary glands of mice injected with 4T1 tumor cells, which were collected using a high-resolution (less than 4 cm −1 ) Raman spectrometer at a fixed (785 nm) laser excitation wavelength and with 60 mW of laser power. The spectra of normal and tumor mammary glands showed consistent differences in the intensity of certain Raman bands and loss of some bands in the tumor spectra. Multivariate statistical methods—principal component analysis (PCA) and discriminant functional analysis (DFA)—were used to separate the data into different groups of mammary tumors, mastitis, lymph nodes contralateral and tumor-cell-injected sides, and normal contralateral and tumor-cell-injected sides. We demonstrate that this spectroscopic technique has the feasibility of discriminating tumor and mastitis from normal tissues and other pathological states in a short period of time and may detect tumor transformation earlier than the standard histological examination stage. Copyright © 2006 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55947/1/1565_ftp.pd

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field