https://indico.ihep.ac.cn//event/9864/

Suyu has presented her JC-102 Paper and the topic was “High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two PhotonAbsorption process (TPA-eTCT)”.

She introduced the TCT, which is a silicon detector by carrier generation using “picosecond laser pulses”. Single Photon Absorption dominated carrier generation is induced along beam path. Laser wavelength is “above Si bandgap” ( λ <= 1150nm). The TPA-TCT, only non-linear absorption is relevant.Femtosecond pulses are needed because TPA absorption probability is significant only for very short pulses. Laser wavelength is below Si bandgap( λ >= 1150nm ). Both have the advantage of good spatial resolution and large penetration depth. She had shown us about the experimental arrangement too that the 3-D scan can be realized by the boundaries of the sensitive volume located in the plane XY and also find the focus point in Z-coordinate.(See figure at page-3). Later she had shown us the experimental results with HVCMOS map and collection charge map and collection time map.

1. Transient currents at each of these regions are compared.
2. Time and charge can reflect the construction.
3. Depletion thickness vs voltage.

So, she conlcuded her talk by saying that Dimension and geometry of the space charge region is measured, computing the effective doping concentration of silicon substrate.

Questions:

Yuhang’s Question: In this paper, it say:”The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam.” and “Very near infrared wavelengths (typically 1064nm) can be collimated to ∼ 5 μm over several mm depth but carriers are generated along the whole beam path lacking point spatial resolution.”Does this mean in TPA-TCT carriers aren’t generated along the whole beam path? Answers:In TPA, focused light generates photocarriers only in a localized volume around the focus. That’s the reason why it’s able to spatially resolve implants.

Xin’s question: The resistivity ρ of the bulk can be calculated by fitting the measured depletion to w(V) (μm) = 0.3 sqrt(ρ)V, could you explain the meaning?Then, what does the nominal 10Ω cm mean? Answer: As I personally think, \pho can be got by fitting as a parameter. Depletion width is 0.01mm, we can get \pho 15Ω by the equation.

Gushan has shown the abstract and the motivation for the next JC-103 Paper,Evidence of a Resonant Structure in the e + e − → π + D^0D^*- Cross Section between 4.05 and 4.60 GeV.