An official website of the United States government
Erbium doped single crystals of lithium niobate were grown within the bulk of 0.075 Er2O3 – 37 Li2O – 37 Nb2O5 – 26 SiO2 glass using a femtosecond pulsed laser. Combined excitation emission spectroscopy was used to show incorporation of erbium into the laser written crystal lattice. Laser power and scanning speed were held constant at optimized values, while bulk sample temperature was systematically varied to study the impact on the crystal growth. Using electron backscatter diffraction to study the transverse cross-sections of grown crystals, control over the lattice rotation rates and crystal size were realized. Unlike changing other parameters, a range of temperatures were found to have substantial impacts on crystal growth, without inhibiting the ability to maintain single crystal formation over long distances.
more »
« less
Transient lattice deformations of crystals studied by means of ultrafast time-resolved x-ray and electron diffraction
Ultrafast lattice deformation of tens to hundreds of nanometer thick metallic crystals, after femtosecond laser excitation, was measured directly using 8.04 keV subpicosecond x-ray and 59 keV femtosecond electron pulses. Coherent phonons were generated in both single crystal and polycrystalline films. Lattice compression was observed within the first few picoseconds after laser irradiation in single crystal aluminum, which was attributed to the generation of a blast force and the propagation of elastic waves. The different time scales of lattice heating for tens and hundreds nanometer thick films are clearly distinguished by electron and x-ray pulse diffraction. The electron and lattice heating due to ultrafast deposition of photon energy was simulated using the two-temperature model and the results agreed with experimental observations. This study demonstrates that the combination of two complementary ultrafast time-resolved methods, ultrafast x-ray, and electron diffraction will provide a panoramic picture of the transient structural changes in crystals.
more »
« less
- Award ID(s):
- 1708717
- PAR ID:
- 10589102
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Structural Dynamics
- Volume:
- 5
- Issue:
- 4
- ISSN:
- 2329-7778
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
A major barrier to defining the structural intermediates that arise during the reversible photointerconversion of phytochromes between their biologically inactive and active states has been the lack of crystals that faithfully undergo this transition within the crystal lattice. Here, we describe a crystalline form of the cyclic GMP phosphodiesterases/adenylyl cyclase/FhlA (GAF) domain from the cyanobacteriochrome PixJ inThermosynechococcus elongatusassembled with phycocyanobilin that permits reversible photoconversion between the blue light-absorbing Pb and green light-absorbing Pg states, as well as thermal reversion of Pg back to Pb. The X-ray crystallographic structure of Pb matches previous models, including autocatalytic conversion of phycocyanobilin to phycoviolobilin upon binding and its tandem thioether linkage to the GAF domain. Cryocrystallography at 150 K, which compared diffraction data from a single crystal as Pb or after irradiation with blue light, detected photoconversion product(s) based on Fobs− Fobsdifference maps that were consistent with rotation of the bonds connecting pyrrole rings C and D. Further spectroscopic analyses showed that phycoviolobilin is susceptible to X-ray radiation damage, especially as Pg, during single-crystal X-ray diffraction analyses, which could complicate fine mapping of the various intermediate states. Fortunately, we found that PixJ crystals are amenable to serial femtosecond crystallography (SFX) analyses using X-ray free-electron lasers (XFELs). As proof of principle, we solved by room temperature SFX the GAF domain structure of Pb to 1.55-Å resolution, which was strongly congruent with synchrotron-based models. Analysis of these crystals by SFX should now enable structural characterization of the early events that drive phytochrome photoconversion.more » « less
-
In this study, the growth of scandium nitride (100) single crystals with high electron mobility and high thermal conductivity was demonstrated by physical vapor transport (PVT). Single crystals were grown in the temperature range of 1900 C–2140 C under a nitrogen pressure between 15 and 20 Torr. Single crystal tungsten (100) was used as a nearly lattice constant matched seed crystal. Growth for 20 days resulted in a 2mm thick crystal. Hall-effect measurements revealed that the layers were n-type with a 300 K electron concentration and a mobility of 2.17 x 1021 cm-3 and 73 cm2/V s, respectively. Consequently, this ScN crystal had a low electrical resistivity, 3.94 x 10- 5 Xcm. The thermal conductivity was in the range of 51–56W/mK, three times higher than those in previous reports for ScN thin films. This study demonstrates the viability of the PVT crystal growth method for producing high quality bulk scandium nitride single crystals.more » « less
-
Abstract Solid‐state packing plays a defining role in the properties of a molecular organic material, but it is difficult to elucidate in the absence of single crystals that are suitable for X‐ray diffraction. Herein, we demonstrate the coupling of divergent synthesis with microcrystal electron diffraction (MicroED) for rapid assessment of solid‐state packing motifs, using a class of chiral nanocarbons—expanded helicenes—as a proof of concept. Two highly selective oxidative dearomatizations of a readily accessible helicene provided a divergent route to four electron‐deficient analogues containing quinone or quinoxaline units. Crystallization efforts consistently yielded microcrystals that were unsuitable for single‐crystal X‐ray diffraction, but ideal for MicroED. This technique facilitated the elucidation of solid‐state structures of all five compounds with <1.1 Å resolution. The otherwise‐inaccessible data revealed a range of notable packing behaviors, including four different space groups, homochirality in a crystal for a helicene with an extremely low enantiomerization barrier, and nanometer scale cavities.more » « less
-
Rutile compounds have exotic functional properties that can be applied for various electronic applications; however, the limited availability of epitaxial substrates has restricted the study of rutile thin films to a limited range of lattice parameters. Here, rutile GeO 2 is demonstrated as a new rutile substrate with lattice parameters of [Formula: see text] and [Formula: see text]. Rutile GeO 2 single crystals up to 4 mm in size are grown by the flux method. X-ray diffraction reveals high crystallinity with a rocking curve having a full width half-maximum of 0.0572°. After mechanical polishing, a surface roughness of less than 0.1 nm was obtained, and reflection high-energy electron diffraction shows a crystalline surface. Finally, epitaxial growth of (110)-oriented TiO 2 thin films on GeO 2 substrates was demonstrated using molecular beam epitaxy. Templated by rutile GeO 2 substrates, our findings open the possibility of stabilizing new rutile thin films and strain states for the tuning of physical properties.more » « less
