We are motivated by the recent measurements of dust opacity indices ( \beta ) around young stellar objects ( YSOs ) , which suggest that efficient grain growth may have occurred earlier than the Class I stage .
The present work makes use of abundant archival interferometric observations at submillimeter , millimeter , and centimeter wavelength bands to examine grain growth signatures in the dense inner regions ( < 1000 AU ) of nine Class 0 YSOs .
A systematic data analysis is performed to derive dust temperatures , optical depths , and dust opacity indices based on single-component modified black body fittings to the spectral energy distributions ( SEDs ) .
The fitted dust opacity indices ( \beta ) are in a wide range of 0.3 to 2.0 when single-component SED fitting is adopted .
Four out of the nine observed sources show \beta lower than 1.7 , the typical value of the interstellar dust .
Low dust opacity index ( or spectral index ) values may be explained by the effect of dust grain growth , which makes \beta < 1.7 .
Alternatively , the very small observed values of \beta may be interpreted by the presence of deeply embedded hot inner disks , which only significantly contribute to the observed fluxes at long wavelength bands .
This possibility can be tested by the higher angular resolution imaging observations of ALMA , or more detailed sampling of SEDs in the millimeter and centimeter bands .
The \beta values of the remaining five sources are close to or consistent with 1.7 , indicating that grain growth would start to significantly reduce the values of \beta no earlier than the late-Class 0 stage for these YSOs .