We analyze femtosecond supercontinuum generation in a distribution of thin solid plates to show that the distributed scheme inhibits processes leading to pulse breakup while allowing spectral expansion to proceed as desired. We introduce basic criteria for setting the plate thickness or initial laser intensity and the location of each plate in the laser beam path and confirm that under these conditions a fully-coherent and intense supercontinuum can be generated for input peak power of as much as two thousand times the critical power for self-focusing of the solid medium.
Based on the frequency-to-time mapping approach, we generate frequency-modulated millimeter-wave (MMW) pulses with central frequencies up to the W-band by a shaped optical pulse excitation of an MMW photonic transmitter with an ultrawide band photodiode as its key component. A coherent detection is achieved via a terahertz time-domain spectroscopic setup. Two different kinds of chirped MMW waveforms are generated; one is a linearly chirped sinusoidal pulse and the other is produced by a frequency-stepped modulation. Through appropriate optical spectral design, the frequency-chirped MMW pulses with instantaneous frequencies sweeping from 120 to 60 GHz, and a time-bandwidth product of ∼25 is experimentally demonstrated.Index Terms-Millimeter wave (MMW), photonic transmitter (PT), pulse shaping, terahertz (THz).
In this work, we study the characteristics of plasma oxynitrided Hf and Zr thin films. A 5-nm-thick Hf or Zr metal film is deposited on the bare Si substrate, followed by plasma oxynitridation on these metal films in a N 2 O or NH 3 ambient. Incorporation of O and N leads to the formation of HfO x N y and ZrO x N y films. The high nitrogen content in the HfO x N y films prepared by NH 3 plasma oxynitridation is found to increase the onset of the crystallization temperature, as compared to films prepared by N 2 O plasma oxynitridation. Nevertheless, the difference in crystallization temperature is not seen for ZrO x N y films. The interlayer ͑IL͒ between HfO x N y ͑or ZrO x N y ͒ and Si is found to be thinner for the films with NH 3 plasma oxynitridation than those with N 2 O plasma oxynitridation. However, the nitrogen incorporated by plasma oxynitridation appears to be depleted after rapid thermal oxidation annealing and is not effective to inhibit the growth of the IL. The activation energy of the IL growth for N 2 O and NH 3 oxynitrided HfO x N y is 0.23 and 0.13 eV, respectively. The activation energy of the IL growth for N 2 O and NH 3 oxynitrided ZrO x N y is 0.19 and 0.14 eV, respectively.Achieving high-performance complementary metal-oxidesemiconductor field-effect transistors drives the downscaling of silicon technology forward. High dielectric constant ͑͒ materials are becoming increasingly favorable due to the exponential increase in tunneling currents with decreasing SiO 2 thickness in the ultrathin regime. Of these, ZrO 2 and HfO 2 are the most promising candidates for their high relative dielectric constant ͑ = 20-25͒ and good thermal stability. Applying high-materials can maintain the same gate capacitance in terms of the equivalent oxide thickness ͑EOT͒ of SiO 2 while decreasing the tunneling current with a thicker physical thickness.However, several issues associated with ZrO 2 and HfO 2 materials for gate-dielectric applications are encountered. For example, while they are thermodynamically stable in contact with Si, an interlayer ͑IL͒ is still generated during the deposition and/or subsequent post-annealing process. 1-3 It reveals that the degree of IL growth is highly dependent on the surface preparation, the deposition, and the post-annealing conditions. Ferrari et al. have shown that short-time annealing is sufficient to form a relatively thick IL by means of injecting oxygen into Si from ZrO 2 and HfO 2 . 4 Therefore, it is suggested that oxide itself is also involved in the fast oxidation of Si at the initial stage. Thermal stability is a critical issue in replacement of conventional SiO 2 gate dielectrics with high-materials. The IL growth as well as the interface reaction are of particular concern in this respect. Accordingly, engineering of the interface becomes a challenging issue in fabricating high-gate dielectrics.Apart from the reduction of the gate dielectric thickness, it is feasible to reduce the EOT by means of reducing the thickness of the IL. Depositing the metal film followe...
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