42 research outputs found
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Kinetics governing phase separation of nanostructured Sn_xGe_(1–x) alloys
We have studied the dynamic phenomenon of Sn_xGe_(1–x)/Ge phase separation during deposition by molecular beam epitaxy on Ge(001) substrates. Phase separation leads to the formation of direct band gap semiconductor nanowire arrays embedded in Ge oriented along the [001] growth direction. The effect of strain and composition on the periodicity were decoupled by growth on Ge(001) and partially relaxed Si_yGe_(1–y)/Ge(001) virtual substrates. The experimental results are compared with three linear instability models of strained film growth and find good agreement with only one of the models for phase separation during dynamic growth
Selective-Area Growth of Heavily \u3cem\u3en\u3c/em\u3e–Doped GaAs Nanostubs on Si(001) by Molecular Beam Epitaxy
Using an aspect ratio trapping technique, we demonstrate molecular beam epitaxy of GaAs nanostubs on Si(001) substrates. Nanoholes in a SiO2 mask act as a template for GaAs-on-Si selective-area growth(SAG) of nanostubs 120 nm tall and ≤100 nm in diameter. We investigate the influence of growthparameters including substrate temperature and growth rate on SAG. Optimizing these parameters results in complete selectivity with GaAsgrowth only on the exposed Si(001). Due to the confined-geometry, strain and defects in the GaAs nanostubs are restricted in lateral dimensions, and surface energy is further minimized. We assess the electrical properties of the selectively grownGaAs nanostubs by fabricating heterogeneous p+–Si/n+–GaAs p–n diodes
Transferred Thin Film Lithium Niobate as Millimeter Wave Acoustic Filter Platforms
This paper reports the first high-performance acoustic filters toward
millimeter wave (mmWave) bands using transferred single-crystal thin film
lithium niobate (LiNbO3). By transferring LiNbO3 on the top of silicon (Si) and
sapphire (Al2O3) substrates with an intermediate amorphous Si (aSi) bonding and
sacrificial layer, we demonstrate compact acoustic filters with record-breaking
performance beyond 20 GHz. In the LN-aSi-Al2O3 platform, the third-order ladder
filter exhibits low insertion loss (IL) of 1.62 dB and 3-dB fractional
bandwidth (FBW) of 19.8% at 22.1 GHz, while in the LN-aSi-Si platform, the
filter shows low IL of 2.38 dB and FBW of 18.2% at 23.5 GHz. Material analysis
validates the great crystalline quality of the stacks. The high-resolution
x-ray diffraction (HRXRD) shows full width half maximum (FWHM) of 53 arcsec for
Al2O3 and 206 arcsec for Si, both remarkably low compared to piezoelectric thin
films of similar thickness. The reported results bring the state-of-the-art
(SoA) of compact acoustic filters to much higher frequencies, and highlight
transferred LiNbO3 as promising platforms for mmWave filters in future wireless
front ends.Comment: 4 pages, 8 figures, accepted by IEEE MEMS 202