A method for assembling a first substrate and a second substrate via metal adhesion layers, the method including: depositing, on a surface of each of the first and second substrates, a metal layer with a thickness controlled to limit surface roughness of each of the deposited metal layers to below a roughness threshold; exposing the metal layers deposited on the surface of the first and second substrates to air; directly adhering the first and second substrates by placing the deposited metal adhesion layers in contact, the surface roughness of the contacted layers being that obtained at an end of the depositing. The adhesion can be carried out in the air, at atmospheric pressure and at room temperature, without applying pressure to the assembly of the first and second substrates resulting from directly contacting the deposited metal adhesion layers.

Methods for preparing layered semiconductor structures are disclosed. The methods may involve pretreating an ion-implanted donor wafer by annealing the ion-implanted donor wafer to cause a portion of the ions to out-diffuse prior to wafer bonding. The donor structure may be bonded to a handle structure and cleaved without re-implanting ions into the donor structure.

A microscale selective laser sintering (-SLS) that improves the minimum feature-size resolution of metal additively manufactured parts by up to two orders of magnitude, while still maintaining the throughput of traditional additive manufacturing processes. The microscale selective laser sintering includes, in some embodiments, ultra-fast lasers, a micro-mirror based optical system, nanoscale powders, and a precision spreader mechanism. The micro-SLS system is capable of achieving build rates of at least 1 cm.sup.3/hr while achieving a feature-size resolution of approximately 1 m. In some embodiments, the exemplified systems and methods facilitate a direct write, microscale selective laser sintering -SLS system that is configured to write 3D metal structures having features sizes down to approximately 1 m scale on rigid or flexible substrates. The exemplified systems and methods may operate on a variety of material including, for example, polymers, dielectrics, semiconductors, and metals.

Methods for preparing layered semiconductor structures are disclosed. The methods may involve pretreating an ion-implanted donor wafer by annealing the ion-implanted donor wafer to cause a portion of the ions to out-diffuse prior to wafer bonding. The donor structure may be bonded to a handle structure and cleaved without re-implanting ions into the donor structure.

When a semiconductor unit is heated, a heater having a flat heating surface is used for performing heating in a state in which a lower surface of an insulated circuit board is placed on the heating surface. When the semiconductor unit is cooled, a cooler having a cooling surface including a pair of support portions is used for performing cooling in which a lower surface of a pair of outer regions of the insulated circuit board are respectively placed to be contact with the pair of support portions, and in which a central region between the pair of outer regions of the insulated circuit board is pressed downward so as to be downward convex.