{TAIL ~ The GaN/substrate bi layer} may be cooled from {HEAD ~ the growth temperature} to an ambient temperature, wherein GaN material cracks laterally and separates from the substrate, forming a free standing article 
{ TAIL ~ The GaN / substrate bi layer } may be cooled from { HEAD ~ the growth temperature } to an ambient temperature , wherein GaN material cracks laterally and separates from the substrate , forming a free standing article
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH