Glass with nanoscale surface features from thermal poling and methods for forming the same

A glass substrate, comprising:

• a first side and an opposite second side;
• an alkali-containing bulk disposed between the first and second sides;
• a first alkali-depleted region formed in the alkali-containing bulk on the first side, the first alkali-depleted region defining at least a portion of a first topographical feature,
• wherein the first topographic feature includes:
• a height extending in a first direction from a base portion of the first topographical feature to an outermost portion of the first topographical feature, the first direction oriented parallel to a thickness of the glass substrate between the first and second sides, and
• a width extending in a second direction between at least two, spaced apart wall portions of the first topographical feature, the second direction oriented normal to the first direction,
• wherein each of the height and the width of the first topographical feature corresponds to a microscale dimension in range from about 1 μm to about 1000 μm;
• a first ion-exchanged region formed in the alkali-containing bulk on the first side;
• a second alkali-depleted region formed in the alkali-containing bulk on the second side;
• and
• a second ion-exchanged region formed in the alkali-containing bulk on the second side,
• wherein:
• the first alkali-depleted region comprises a first thickness t1;
• the second alkali-depleted region comprises a second thickness t2;
• the first ion-exchanged region comprise a third thickness t3 substantially equal to t1;
• and
• the second ion-exchanged region comprises a fourth thickness t4.