Showing papers by "S.E. Holland published in 2000"

Back-illuminated, fully-depleted CCD image sensors for use in optical and near-IR astronomy

Abstract: Charge-coupled devices (CCDs) of novel design have been fabricated at Lawrence Berkeley National Laboratory (LBNL), and the first large-format science-grade chips for astronomical imaging are now being characterized at Lick Observatory. They are made on 300-μm thick n-type high-resistivity ( ∼10 000 Ω cm ) silicon wafers, using a technology developed at LBNL to fabricate low-leakage silicon microstrip detectors for high-energy physics. A bias voltage applied via a transparent contact on the back side fully depletes the substrate, making the entire volume photosensitive and ensuring that charge reaches the potential wells with minimal lateral diffusion. The development of a thin, transparent back-side contact compatible with fully depleted operation permits blue response comparable to that obtained with thinned CCDs. Since the entire region is active, high quantum efficiency is maintained to nearly λ=1000 nm , above which the silicon band gap effectively truncates photoproduction. Early characterization results indicate a charge transfer efficiency >0.999995, readout noise 4 e's at −132°C, full well capacity >300 000 e 's, and quantum efficiency >85% at λ=900 nm .

A 2K×2K High Resistivity CCD

Abstract: We present new results from the characterisation of a fully depleted 2048-row by 2048-column (2K×2K) CCD on high resistivity silicon. The CCD was fabricated at the Lawrence Berkeley National Laboratory (LBNL). This device represents a one hundred-fold increase in CCD size compared to devices previously made at LBNL. The large CCD size allows us to do accurate charge transfer efficiency measurements. A two-layer antireflection coating is modelled and compared with laboratory measurements of both quantum efficiency and reflectivity.

Performance of a compact 64-pixel CsI(Tl)/Si PIN photodiode imaging module with IC readout

Abstract: Summary form only received as follows: The authors present performance measurements for a complete 64-pixel compact gamma camera imaging module consisting of optically isolated 3/spl times/3/spl times/5 mm/sup 3/ CsI(Tl) crystals coupled to a custom array of low-noise Si PIN photodiodes read out by a custom IC. The custom 64-pixel photodiode arrays at 50 V bias demonstrate an average leakage current of 98% yield of pixels with <100 pA leakage, and a quantum efficiency of 75% for 540 nm CsI(Tl) scintillation photons. The custom 64-channel readout IC uses low-noise preamplifiers, shaper amplifiers, and a winner-take-all (WTA) multiplexer. Prototype ICs demonstrate low noise of 180 e- rms at 8 ms peaking time with a photodiode load (3 pF, 50 pA). Prototype detector modules using prototype ICs and prototype 12-pixel photodiode arrays yield an average room temperature energy resolution of 10.7% for the 140 keV gammas from /sup 99m/Tc. Intrinsic spatial resolution is determined almost entirely by the 3/spl times/3 mm/sup 2/ pixel size, and system spatial resolution depends on the collimator employed for the chosen application (e.g., scintimammography).