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首页> 外文学位 >Interaction of 157-nm excimer laser light with fused silica, polytetrafluoroethylene and calcium fluoride.
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Interaction of 157-nm excimer laser light with fused silica, polytetrafluoroethylene and calcium fluoride.

机译：157 nm准分子激光与熔融石英，聚四氟乙烯和氟化钙的相互作用。

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摘要

Emission of positive ions, neutral atoms and molecules and negative ions was observed during 157-nm irradiation of fused silica. Positive ion emission from fused Silica is best explained by a hybrid mechanism involving (a) excitation of an antibonding chemical state (Menzel-Gomer-Redhead mechanism) and (b) acceleration of the positive ion by repulsive electrostatic forces due to the photoionization of nearby electron traps. Neutral emission results from the absorption of single 157 nm photons that cleave strained bonds to produce defects that subsequently diffuse to the surface. There then react with dangling bonds to release neutral atoms and molecules. Negative ions are created after the laser pulse, by electron attachment to the neutral particles.;Time- and mass-resolved measurements on neutral particles emitted PTFE during exposure to 157-nm laser radiation. We observe neutral (CF2) N radicals for all N up to the limit of our mass filter (N = 6). These radicals are emitted directly from the surface with high kinetic energies of about 0.6 eV of the fastest (CF2)N radicals consistent with photochemical scission of the polymer backbone. A great majority of emitted material is in the form of heavier fragments ranging from 300 to 2000 amu. The presence of heavy and light particles in the cloud of emitted particles gives rise to some unique behavior in the way it expands. The trajectories of the v heaviest fragments are preferentially directed at large angles away from the surface normal---often nearly parallel to the substrate surface. This behavior is due to density and pressure gradients associated with the Gaussian intensity profile of the laser beam.;Transient absorption was observed in Calcium Fluoride during 157-nm irradiation with peaks at 153 nm, 220 nm and 375 nm under 157-nm irradiation due to the Hs- center, Ca1+ interstitial and the F-center respectively. Capture of a hole by Hs- center, Ca1+ interstitial destroys the absorption and trapping of an electron at Hi0 center and the Ca2+ interstitial re-induces absorption. Aggregation of F-centers to form M-centers leads to loss of absorption at 375 nm and the dissociation of the M-center when irradiation is restored re-induces absorption.
机译：在熔融石英的157 nm照射过程中观察到正离子，中性原子和分子以及负离子的发射。熔融二氧化硅的正离子发射最好用一种混合机理来解释，该机理包括：（a）激发一种反键化学态（Menzel-Gomer-Redhead机理），以及（b）由于附近的光电离而产生的排斥静电力使阳离子加速电子陷阱。中性发射源于单个157 nm光子的吸收，这些光子裂解了应变键，产生了随后扩散到表面的缺陷。然后在那里与悬挂键反应以释放中性原子和分子。负离子是在激光脉冲之后通过电子附着到中性粒子上而产生的。对暴露于157 nm激光辐射期间发射PTFE的中性粒子的时间和质量分辨测量。我们观察到所有N的中性（CF2）N自由基达到我们的质量过滤器的限制（N = 6）。这些自由基以最快的（CF2）N自由基的约0.6 eV的高动能直接从表面发出，这与聚合物主链的光化学断裂一致。大部分散发的物质以重碎片的形式存在，范围在300至2000 amu之间。在发射的粒子云中，重粒子和轻粒子的存在会引起其扩展方式的某些独特行为。最重的碎片的轨迹优先指向远离表面法线的大角度-通常与基材表面几乎平行。此行为是由于与激光光束的高斯强度分布相关的密度和压力梯度引起的;在157 nm辐照期间氟化钙中观察到瞬态吸收，由于在157 nm辐照下在153 nm，220 nm和375 nm出现了峰值分别位于Hs-中心，Ca1 +间隙和F-中心。通过Hs-中心捕获空穴，Ca1 +间隙破坏了电子的吸收，并在Hi0中心捕获了电子，而Ca2 +间隙重新诱导了吸收。 F中心的聚集形成M中心会导致375 nm处的吸收损失，并且在恢复辐照后M中心的解离会重新诱导吸收。

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  • 作者

    George, Sharon Rose.;

  • 作者单位

    Washington State University.;

  • 授予单位 Washington State University.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 197 p.
  • 总页数 197
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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