  Scientific Complementary Metal Oxide Semiconductor (sCMOS) sensors are
finding increasingly more applications in astronomical observations, thanks to
their advantages over charge-coupled devices (CCDs) such as a higher readout
frame rate, higher radiation tolerance, and higher working temperature. In this
work, we investigate the performance at the individual pixel level of a
large-format sCMOS sensor, GSENSE1516BSI, which has 4096 * 4096 pixels, each of
15 {\mu}m in size. To achieve this, three areas on the sCMOS sensor, each
consisting of 99 * 99 pixels, are chosen for the experiment. The readout noise,
conversion gain and energy resolutions of the individual pixels in these areas
are measured from a large number (more than 25,000) of X-ray events accumulated
for each of the pixels through long time exposures. The energy resolution of
these pixels can reach 140 eV at 6.4 keV at room temperature and shows a
significant positive correlation with the readout noise. The accurate gain can
also be derived individually for each of the pixels from its X-ray spectrum
obtained. Variations of the gain values are found at a level of 0.56%
statistically among the 30 thousand pixels in the areas studied. With the gain
of each pixel determined accurately, a precise gain correction is performed
pixel by pixel in these areas, in contrast to the standardized ensemble gain
used in the conventional method. In this way, we could almost completely
eliminate the degradation of energy resolutions caused by gain variations among
pixels. As a result, the energy resolution at room temperature can be
significantly improved to 124.6 eV at 4.5 keV and 140.7 eV at 6.4 keV. This
pixel-by-pixel gain correction method can be applied to all kinds of CMOS
sensors, and is expected to find interesting applications in X-ray
spectroscopic observations in the future.
