US 12,281,992 B1
Systems and methods for voltage contrast imaging using photoreflectance microscopy
William W. Chism, II, Austin, TX (US)
Filed by William W. Chism, II, Austin, TX (US)
Filed on Jul. 30, 2022, as Appl. No. 17/877,928.
Claims priority of provisional application 63/360,159, filed on Sep. 13, 2021.
Int. Cl. G01N 21/55 (2014.01); G01N 21/95 (2006.01)
CPC G01N 21/9505 (2013.01) [G01N 21/55 (2013.01); G01N 2201/06113 (2013.01)] 14 Claims
OG exemplary drawing
 
1. An apparatus for acquiring spatially resolved photoreflectance data, comprising:
(a) a first laser source operable to provide an amplitude modulated pump laser beam suitable for inducing time periodic changes in the reflectance of a sample;
(b) a second laser source operable to provide a continuous wave probe laser beam suitable for detecting pump induced changes in the reflectivity of the sample;
(c) an optical system operable to focus the pump laser beam and the probe laser beam onto a surface of the sample, and to collect and project probe light reflected from the sample to a back focal plane;
(d) a position sensitive detector, comprising a plurality of spatially arranged photosensor elements, fixtured at the back focal plane and operable to generate a plurality of electrical signals proportional to an input probe light intensity;
(e) a multichannel lock-in amplifier operable to output a plurality of demodulated signals corresponding to the plurality of electrical signals; and
(f) a computer operable to receive and record the plurality of demodulated output signals, said plurality comprising spatially resolved photoreflectance data.
 
7. A method of acquiring spatially resolved photoreflectance data, the method comprising the steps of:
(a) directing an intensity modulated pump laser beam onto a surface of a sample to produce a time periodic modulation of the reflectance of the sample;
(b) focusing a second probe laser beam onto at least a portion of the area obtaining the time periodic modulation of the reflectance, wherein the probe laser beam comprises at least one wavelength suitable for detecting the induced changes in the reflectivity of the sample;
(c) collecting probe light reflected from the sample and projecting it onto a position sensitive detector fixtured at a back focal plane to generate a plurality of electrical signals corresponding to changes in reflected probe light intensity as a function of position;
(d) demodulating the plurality of electrical signals using a plurality of demodulation circuits, said plurality of demodulated signals comprising spatially resolved photoreflectance data; and
(e) recording the spatially resolved photoreflectance data.